Inflorescence diversity and evolution in the PCK Clade (Poaceae: Panicoideae: Paniceae)

R. Reinheimer; A. C. Vegetti

The new genus Kellochloa is proposed, on the basis of morphological and molecular characters, in order to include two North American species of Panicum s.l., previously classified in sect. Verrucosa: P. brachyanthum and P. verrucosum. Both species are annual, with decumbent culms branching divaricately at the lower nodes, and erect culms with terminal and axillary inflorescences, with pilose spikelets, lower glume 1/6 to 1/4 the length of the spikelet, upper glume and lower lemma subequal, 3–5-nerved, the lower anthecium reduced to the lower lemma, and upper anthecium indurate, with bicellular microhairs and simple papillae evenly distributed all over the lemma and palea. Molecular phylogenetic studies, analyzing plastid ndhF and rpoA sequences, confirmed that these morphological characters are differencial. The phylogenetic position and taxonomic features of the new genus are established and compared with Panicum s.str. and other taxa of the Sacciolepis-Trichanthecium clade. Full synonymies and descriptions, a distribution map, illustrations of both species, and a key are provided. Two new combinations are proposed. In addition, four African ungrouped species of Panicum s.l. were, for the first time, included in the phylogenetic analysis in order to analyze their relationship with the new genus and its positions in the Sacciolepis-Trichanthecium clade.

Panicum scabridum, an incertae sedis species of Panicum s.l., is here included in the genus Coleataenia, following a phylogenetic analysis based on one new ndhF sequence of the species and associated morphological data. Panicum scabridum and species of Coleataenia are cespitose and perennial plants, with a lower glume (1–)3–5-nerved, 1/3 to 3/4 of the spikelet, upper glume and lower lemma 5–9-nerved, and upper anthecium smooth, shiny, and indurate. Within Coleataenia, P. scabridum appeared as the sister taxon of the species pair C. prionitis and C. petersonii; these three species are the only NADP-me taxa of tribe Paspaleae exhibiting two bundle sheaths around the vascular bundles, i.e., with an outer parenchymatous sheath and an inner mestome sheath with specialized chloroplasts. The new combination

The genus Louisiella (Poaceae, Paniceae) is reviewed. This African monotypic genus was originally circumscribed on the basis of morphological characters. Recent phylogenetic studies have shown its affinity with an American species of Panicum, P. elephantipes. Molecular, morphological, and anatomical characters of Louisiella fluitans and P. elephantipes were analyzed. Both species share vegetative and reproductive characters, including habit, ligules, blades, inflorescence, and spikelet features, such as a reduced lower glume, lanceolate upper glume and lower lemma both longer than the upper anthecium, lower palea reduced or absent, and lower flower absent, upper anthecium indurate, and a caryopsis with a linear hilum. Anatomically, both taxa are Kranz of the PS-subtype, with specialized chloroplasts on the outer parenchymatous sheath. The molecular phylogenetic analysis also corroborates the relationship between these species, with a 100% bootstrap support. As a result, we conclude that P. elephantipes has to be transferred to Louisiella, making that genus amphitropicalin distribution. Affinities of Louisiella with other genera of Paniceae are also discussed. Finally, two lectotypes are designated for Panicum fistulosum and Digitaria megapotamica.

Plant Syst Evol (2008) 275:133–167 DOI 10.1007/s00606-008-0057-4 ORIGINAL ARTICLE Inflorescence diversity and evolution in the PCK Clade (Poaceae: Panicoideae: Paniceae) R. Reinheimer Æ A. C. Vegetti Received: 10 September 2007 / Accepted: 29 April 2008 / Published online: 18 July 2008 Ó Springer-Verlag 2008 Abstract The PCK Clade, represented by six to nine genera, is a monophyletic group situated within the Paniceae tribe. The highly diverse inflorescences within the PCK Clade provide an interesting system for the study of morphological evolution and also may aid in better understanding its unclear systematics. The inflorescence structure of 110 members of the PCK Clade has been investigated. Inflorescences are polytelic showing different levels of truncation. At least 21 different inflorescence subtypes were identified. Fourteen variable inflorescence characters were found, among which some have suprageneric or infrageneric value and others are polymorphic. A key for the identification of inflorescence types is presented. Nine processes have been identified as responsible for inflorescence diversification. Highly branched inflorescences with different internode lengths are present in the basal genus whereas truncated inflorescence morphologies appear late in the history of the clade. The precise timing of morphological changes is impossible to assess until we have a well supported phylogeny for the PCK Clade. Keywords PCK Clade Grasses Inflorescence morphology Evolution Typology SEM R. Reinheimer A. C. Vegetti Cátedra de Morfologı́a Vegetal, Facultad de Ciencias Agrarias, Universidad Nacional del Litoral, Esperanza, Santa Fe, Argentina R. Reinheimer (&) Department of Biology, University of Missouri of Saint Louis, One University Blvd, St Louis, MO 63121, USA e-mail: reinheimerr@umsl.edu; renatarein@fca.unl.edu.ar Introduction The Poaceae (grass) family is one of the most important groups among the angiosperms in terms of its morphological diversity, systematics, ecology and economic importance (Clayton and Renvoize 1986; Grass Phylogeny working Group 2001). The family includes about 10,000 species divided into 12 subfamilies and over 700 genera (Tzvelev 1989; Renvoize and Clayton, 1992; Watson and Dallwitz 1992; Jacobs et al. 1999; Grass Phylogeny working Group 2001). The grasses are widespread all over the world and are the principal component of human intake since among its species are sugar cane and cereal crops (such as maize, rice, oats, wheat, etc.) (Tzvelev 1989; Renvoize and Clayton 1992; Watson and Dallwitz 1992; Jacobs et al. 1999; Grass Phylogeny working Group 2001). Morphologically, the grasses diverge from the rest of the monocots by having a unique fruit (caryopsis), a highly differentiated lateral embryo, the pollen wall without scrobiculi and a unique floral morphology. The typical grass flower consists of a pistil, three stamens and two lodicules (second whorl organs) subtended by a palea and a lemma (outer second whorl), the whole unit being known as a floret (Irish 1998; Schmidt and Ambrose 1998; Soreng and Davis 1998; Ambrose et al. 2000; Grass Phylogeny working Group 2001). A spikelet may bear one to forty florets subtended by two sterile bracts (the lower and upper glumes). The spikelets are placed on extensively variable inflorescence ramification systems, which were classically but inaccurately named as ‘‘spikes’’, ‘‘spicate racemes’’ or ‘‘panicles’’. The grass inflorescence is considered as a novel structure among the angiosperms and many authors have emphasized its agronomic, taxonomic and phylogenetic importance (Pensiero and Vegetti 2001; Rua 1993, 123 134 1996, 2003a, b; Vegetti and Anton 1995, 2000; Friedman and Harder 2005). The PCK Clade is a well supported monophyletic group of grasses situated within the subfamily Panicoideae and more specifically inside the x = 9 clade of the Paniceae tribe (Gómez-Martinez and Culham 2000; Zuloaga et al. 2000; Duvall et al. 2001; Giussani et al. 2001). All members of the PCK Clade are C4 plants; the leaf anatomy reflects a PEP-ck physiology (phosphoenol pyruvate carboxykinase, PCK), which is a synapomorphy for the clade (Gómez-Martinez and Culham 2000; Zuloaga et al. 2000; Duvall et al. 2001; Giussani et al. 2001). Also, species of the clade share a mucronate or aristulate upper lemma and different ornamentation patterns and textures of the upper anthecium (Morrone and Zuloaga 1992, 1993). The PCK Clade is represented by six to nine genera [Brachiaria (Trin.) Griseb., Chaetium Nees, Eccoptocarpha Launert, Eriochloa Kunth, Megathyrsus (Pilg.) B.K. Simon and S.W.L. Jacobs, Melinis P. Beauv., Thuarea Pers., Urochloa P. Beauv. and Yvesia A. Camus] depending on the author of the revision (Clayton and Renvoize 1986; Frank 1998; Gómez-Martinez and Culham 2000; Zuloaga et al. 2000; Duvall et al. 2001; Giussani et al. 2001; Torres González and Morton 2005). Among them, Brachiaria and Urochloa are the most important, in terms of number of species. The Brachiaria-Urochloa complex includes about 100 species distributed across the Old and the New World (Frank 1998; Torres González and Morton 2005). The majority of the species are found in Tropical Africa, with some in America and Asia; the group is rare in Europe (Clayton and Renvoize 1982 1986; Watson and Dallwitz 1992; Morrone and Zuloaga 1992, 1993; Veldkamp 1996a, 2004; Frank 1998; Torres González and Morton 2005). Other genera in the group have one or only a few species. Thuarea is paleotropical and represented by two species, T. perrieri A. Camus, an annual species from Madagascar and T. involuta (G. Forst.) R. Br. ex Sm., an important perennial weed that grows in Indomalesia, Northern Australia and New Guinea (Watson and Dallwitz 1992). Yvesia is monotypic, represented by the annual species Y. madagascariensis A. Camus, originally from Madagascar. Eccoptocarpha is also monotypic, containing only the annual caespitose species E. obconiciventris Launert, which is found in Tropical African savannas (Watson and Dallwitz 1992). Chaetium is an American genus with three perennial caespitose species found from México, Central America and Cuba, to Northern South America (Morrone et al. 1998). Megathyrsus maximum (Jacq.) B.K. Simon and S.W.L. Jacobs (also known as Panicum maximum Jacq. or Urochloa maxima (Jacq.) R.D. Webster) (Giussani et al. 2001; Aliscioni et al. 2003; Simon and Jacobs 2003) is an African forage species but 123 R. Reinheimer, A. C. Vegetti also a weed, widely cultivated in tropical and subtropical regions around the World. Eriochloa is a pantropical genus that includes about 25– 30 annual and perennial species (Clayton and Renvoize 1986; Nicora and Rúgolo de Agrasar 1987; Arriaga 2000). Melinis is a paleotropical genus with about 12 annual or perennial species, among which one or two grow in South America and West India and the rest are found in South Africa and Madagascar (Clayton and Renvoize 1986; Nicora and Rúgolo de Agrasar 1987; Zizka 1988; Watson and Dallwitz 1992). Despite efforts by many authors, the phylogeny of the PCK clade remains poorly resolved (Frank 1998; GómezMartinez and Culham 2000; Zuloaga et al. 2000; Duvall et al. 2001; Giussani et al. 2001; Aliscioni et al. 2003; Torres González and Morton 2005). Moreover, the taxonomic delimitation of Brachiaria and Urochloa is not clear, with no evidence to support the monophyly of either genus (Beauvois 1812; Trinius 1826; Grisebach 1853; Nash 1903; Stapf 1920; Hughes 1923; Henrard 1941; Clayton and Renvoize 1982; Webster 1987, 1988; Davidse 1993; Morrone and Zuloaga 1991, 1992, 1993; Veldkamp 1996a, 1996b, 2004; Frank 1998; Nelson and Fernández 1998; López-Ferrari and Espejo Serna 2000; Giussani et al. 2001; Wunderlin and Hansen 2001; Sharp and Simon 2002; Zuloaga and Morrone 2003; Torres González and Morton 2005). The PCK Clade exhibits extensive morphological variation. The inflorescences are highly diverse and several genera have unique inflorescence characters (Fig. 1). Within the clade, the inflorescence varies from lax panicles to simple inflorescences made up of a few racemes (Shaw and Smeins 1984; Clayton and Renvoize 1986; Davidse 1987; Nicora and Rúgolo de Agrasar 1987; Thompson et al. 1990; Morrone and Zuloaga 1992; Watson and Dallwitz 1992; Frank 1998; Morrone et al. 1998; Arriaga 2000). The morphological diversity of the PCK Clade provides an interesting system for study the evolution of morphology and also may aid in better understanding of the phylogeny and taxonomy of the genera. Inflorescence characters have been used successfully in multiple studies, in which the main goals were to understand evolution and taxonomy (Rua 1993, 1996; Vegetti and Anton 1995, 2000; Kellogg 2000; Pensiero and Vegetti 2001; Doust and Kellogg 2002a, 2002b; Rua 2003a; Doust and Drinnan 2004; Kellogg et al. 2004; Bess et al. 2005; Liu et al. 2005). In this study, we investigated inflorescence structure in the PCK Clade as a part of a larger project addressing morphological evolution in the clade using the study of adult morphology, development and its genetic bases (Reinheimer 2007). We had four goals: (1) to describe inflorescence structure in the PCK Clade; (2) to identify new characters to include in future phylogenetic studies, Inflorescence diversity and evolution in the PCK Clade (Poaceae) 135 Fig. 1 Mature inflorescence variation in the PCK Clade. a U. mollis; b U. distachya; c U. ruziziensis; d U. lata; e U. xantholeuca; f U. plantaginea; g U. paucispicata; h U. platyphylla; i U. jubata; j U. mosambicensis; k E. punctata; l M. repens; m U. leucacrantha; n U. panicoides; o U. lachnantha; p B. eruciformis (3) to discuss their implications in relation to taxonomy in the clade and, (4) to suggest some processes responsible for inflorescence diversity in the group. Materials and methods Live plants from field collections and seed banks (CIAT) (cultivated at the greenhouse of the Agronomy School of the University of Litoral, Argentina) and herbarium specimens from eight different herbaria [CTS, J, LIL, SI, y SF, NY, MO, US (abbreviations from Index Herbariorum, ref.)] were studied under a stereoscopic microscope (Table 1). One-hundred and ten species were selected; among which 91 belong to the Brachiaria-Urochloa complex, while 19 are members of other genera in the clade (Megathyrsus, Eriochloa, Melinis, Chaetium, Yvesia and Thuarea). Eccoptocarpha obconiciventris was not 123 136 R. Reinheimer, A. C. Vegetti Table 1 Material studied and the most common synonyms for each species Species Synonyms Voucher Brachiaria ambigens Chiov. ex Chiarugi Brachiaria chusqueoides (Hack.) Clayton Brachiaria clavipila (Chiov.) Robyns Brachiaria coronifera Pilg. Brachiaria dimorpha A. Camus Brachiaria epacridifolia (Stapf) A. Camus Brachiaria eruciformis (Sm.) Griseb. _ Bojdan AB–300; Richards 23564 (MO) Panicum chusqueoides Hack Gillett 13143 (MO) Panicum clavipilum Chiov. Milne-Redhead 2692 (US); Robison 3390 (US) _ _ Panicum epacridifolium Stapf Schlieben 768 (US) 13565 (LIL); Humbert 3879 (US) Bosser 2714 (MO) Brachiaria erucaeformis (Sm.) Griseb.; Brachiaria isachne (Roth ex Roem. and Schult.) Stapf; Echinochloa eruciformis (Sm.) Koch; Echinochloa eruciformis (Sm.) Rchb.; Milium alternans Bubani; Moorochloa eruciformis (Sm.) Veldkamp; Panicum anisostachium Bojer; Panicum caucasicum Trin.; Panicum cruciforme Sibth. ex Roem. ex Schult.; Panicum eruciforme Sm.; Panicum isachne Roth ex Roem. and Schult.; Panicum isachne var. mexicana Vasey ex Beal; Panicum pubinode Hochst. ex A. Rich.; Panicum wightii Nees Velez I. 3039; Hitchcock 708 (LIL) (MO); 813806 (MO); 1906505 (MO); 2875544 (MO); 2876668 (MO); 2876671 (MO); 2876672 (MO); 2876789 (MO); 3940159 (MO); 3943569 (MO); 04984290 (MO); Abbas et Mokntar 95 (MO); Aellen 13/08/ 1948, 26/06/1948 (MO); Ament 482 (MO); Aretto 8529 (MO); Bosser 10549 (MO); Brain 944 (MO); Bush 390 (MO); Collenette 8375 (MO); Davidse 6708 (MO); Davidse et Simon 6451 (MO); De Wilde c.s. 5682, 6010 (MO); du Toit 522 (MO); Faden et Faden 74/739 (MO); Fasberg 39198, 59654 (MO); Giffen s/n (MO); Gonde 150, 287 (MO); Gould 15016 (MO); Herbst 46 (MO); Hunttey 14832 (MO); Jermy s/n (MO); Kemp 6650 (MO); Kiriken 448 (MO); Leistner 1243 (MO); Loutfy 1 Nov. 1976, 10312 (MO); Mackee 196, 30762, 42883, 43764 (MO); Pappi 1355, 2436 (MO); Parrignahi 5761 (MO); Phillipson 1050 (MO); Rattray 1649 (MO); Roemer s/n (MO); Russell 2744 (MO); Sáenz et Morrone 260 (MO) (SI); Sandwith 24 (MO); Schimper 1855, 1868 (MO); Smith 3072, 3375, 3497 (MO); Smook 1545, 2143, 2842, 6246, 6296, 6463, 622 (US); 8407 (US) Mitchell 14/22 (US) Decary 8546 (US); Humbert 14162 (US) Faden et Faden 71/807 (US); Robertson 6142 (US) Seydel 3141 (MO) Brachiaria grossa Stapf Brachiaria humbertiana A. Camus Brachiaria longiflora Clayton Brachiaria malacodes (Mez and K. Schum.) H. Scholz Brachiaria marlothii (Hack.) Stent Brachiaria ovalis Stapf Brachiaria pseudodichotoma Bosser Brachiaria pubifolia Stapf Brachiaria pungipes Clayton Brachiaria rugulosa Stapf Brachiaria scalaris Pilg. Brachiaria schoenfelderi C.E. Hubb. and Schweick. 123 Panicum nudiglume var. major Rendle _ _ Brachiaria poaeoides Stapf; Moorochloa malacodes (Mez and K. Schum.) Veldkamp; Panicum malacodes Mez and K. Schum. Panicum marlothii Hack. Brachiaria glauca Stapf; Brachiaria somalensis C.E. Hubb; Panicum nudiglume var. major Balf. f.; Panicum ovale R. Br. _ Brachiaria xantholeuca (Hack. ex Schinz) Stapf; Panicum pubifolium Mez; Panicum pubifolium Nash _ Brachiaria umboensis Stent and Rattray Brachiaria heterocraspeda (Peter) Pilg.; Brachiaria pilgerana H. Scholz; Panicum heterocraspedum Peter; Panicum scalare Mez; Panicum scalarum Schweinf. Moorochloa schoenfelderi (C.E. Hubb. and Schweick.) Veldkamp Mennell Feb.1930 (US); Smook 2882 (US); Wilman s/n (US), 7109 (US) Gilbert et Gilbert 2324 (MO) Phillipson et Rabesihanaka 3180 (US) Greenway et Kamuri 13529, 13940 (MO) Williamson 1865 (MO) Robertson 3238 (MO) Chongo 14 (LIL); Junifer et Gefford 201 (LIL); Schlieben 643, 768, 1031 (LIL); Bogdan AB-5306 (US); Webster McCallum 119 (US) Dinter 7438 (US); Giess et al. 6438 (MO); Schuwrickedt 2051 (US); Volk s/n (US) Inflorescence diversity and evolution in the PCK Clade (Poaceae) 137 Table 1 continued Species Synonyms Voucher Brachiaria serrata (Thunb.) Stapf Pappi 50, 460 (LIL); Bogdan AB-4165 (US); Godfrey SH-1571 (US); Golddamith 6/56 (US) serrifolia (Hochst.) Brachiaria brachylopha Stapf; Holcus serratus Thunb.; Brachiaria serrata var. gossypina (A. Rich.) Stapf; Brachiaria serrata var. serrata Stapf; Panicum gossypinum A. Rich.; Panicum nigropedatum var. basipiliferum Chiov.; Panicum scopuliferum Trin.; Panicum serratum (Thunb.) Spreng.; Panicum serratum var. brachylophum (Stapf) A. Chev.; Panicum serratum var. gossypinum Hack. ex T. Durand and Schinz; Panicum serratum var. hirtum Kuntze; Panicum serratum var. holosericeum Hack. ex T. Durand and Schinz; Sorghum serratum (Thunb.) Roem. and Schult.; Tricholaena abbreviata K. Schum. ex Engl. Panicum serrifolium Hochst. stigmatisata (Mez) Panicum stigmatisatum Mez tsiafajavonensis A. _ umbelata (Trin.) Panicum nossibense Steud.; Panicum umbellatum subsp. nossibense (Steud.) A. Camus; Panicum umbellatum Trin. _ _ Brachiaria Stapf Brachiaria Stapf Brachiaria Camus Brachiaria Clayton Brachiaria umbralitis Napper Brachiaria urocoides S.L.Chen and Y.X.Jin Chaetium bromoides (J. Presl) Benth. ex Hemsl. Chaetium cubanum (C. Wright) Hitchc. Eriochloa aristata Vasey Eriochloa distachya Kunth Eriochloa grandiflora (Trin.) Benth. Eriochloa mollis (Michx.) Kunth Eriochloa montevidensis Griseb. Berchtoldia bromoides J. Presl; Panicum berchtholdiae Döll Perotis cubana C. Wright Eriochloa boxiana Hitchc.; Eriochloa punctata var. aristata (Vasey) M.E. Jones Eriochloa tridentata (Trin.) Kuhlm.; Helopus brachystachys Trin.; Paspalum brachystachyum (Trin.) Trin.; Paspalum tridentatum Trin. Helopus grandiflorus Trin.; Paspalum ctenostachyum Trin. Eriochloa michauxii (Poir.) Hitchc.; Eriochloa michauxii var. Michauxii; Panicum molle Michx. Eriochloa montevidensis fo. subcolorata Hack.; Eriochloa punctata var. montevidense (Griseb.) Herter; Eriochloa punctata var. montevidensis (Döll) Herter; Helopus annulatus var. montevidensis Döll Aliyssimia 10 83 (US); HItchcock 24680 (US); Schimper 1083 (US) Menzirgen et Conert 343, 586 (LIL); Adam 15072 (US); Mensah SLUS/565 (US) Humbert 13447a, 13447b (LIL); Decary et al. s/n (US) Robinson 5365 (US); Vaughan A-11 (US) Hitchcock 25024 (US) Volk 501, 510 (US) Arséne 39359 (LIL); Hitchcock s/n (LIL); Pringle 11736 (LIL); Hitchcock 8440 (SI); Matuda et al. 29718 (SI) Ekman 796 (LIL); Clark L. G. s/n (ISC) Warren 23060 (SI) Beck 6961 (SI); Killeen 244 (SI); Scolnik et Luti 738 (SI) Dusén 16865 (SI); Fontana 117-7 (SI); Jorgensen 4783 (SI) Fredholm 6097 (SI) Covas et Ragonese 3904 (SF); Pensiero et Marino 3574 (SF); Pire et Nisensohn 191 (SF); Ragonese 2118, 3188, 3310 (SF); Vegetti 24 (SF); Burkart 18405 (SI); Burkart et Troncoso 11432 (SI); Cabrera 7482 (SI); Cabrera et al. 27530 (SI); Nicora 4688 (SI); Rosengurtt B-5483, B-5503 (SI); Schinini 6283 (SI); Werdermann 715 (SI); Zuloaga 3027 (SI); Zuloaga et Deginani 3693a (SI) 123 138 R. Reinheimer, A. C. Vegetti Table 1 continued Species Synonyms Voucher Eriochloa polystachya Kunth Eriochloa punctata var. subglabra (Nash) Urb.; Eriochloa subglabra (Nash) Hitchc.; Helopus polystachys (Kunth) Trin. ex Steud.; Milium polystachyon (Kunth) Spreng.; Monachne subglabra Nash; Paspalum polystachyum (Kunth) Raspail Agrostis procera Retz.; Agrostis ramosa (Retz.) Poir.; Eriochloa annulata (Flüggé) Kunth; Eriochloa hackelii Honda; Eriochloa polystachya Hook. f.; Eriochloa polystachya var. annulata (Flüggé) Maiden & Betche; Eriochloa ramosa (Retz.) Kuntze; Eriochloa ramosa var. barbata Peter; Helopus annulatus (Flüggé) Nees; Helopus laevis Trin.; Helopus pilosus Trin.; Milium ramosum Retz.; Paspalum annulatum Flüggé; Piptatherum annulatum (Flüggé) J. Presl; Thysanolaena procera (Retz.) Mez. Agrostis decipiens Salzm. ex Steud.; Agrostis punctata (L.) Lam.; Eriochloa kunthii G. Mey.; Eriochloa montevidensis Griseb.; Eriochloa polystachya var. punctata (L.) Maiden & Betche; Eriochloa punctata f. intermedia Parodi; Eriochloa punctata Hochst. ex Steud.; Eriochloa punctata var. montevidense (Griseb.) Herter; Eriochloa punctata var. parodii Herter; Eriochloa punctata var. punctata; Helopus cognatus Steud.; Helopus kunthii (G. Mey.) Trin. ex Steud.; Helopus punctatus (L.) Nees; Helopus punctatus var. cognatus (Steud.) Döll; Milium punctatum L.; Monachne punctata (L.) Nash; Oedipachne punctata (L.) Link; Paspalum punctatum (L.) Flüggé; Paspalus punctatus (L.) Flüggé; Piptatherum punctatum (L.) P. Beauv. Eriochloa filifolia Hitchc.; Piptatherum setosum A. Rich.; Eriochloa villosa var. stenantha Ohwi; Helopus villosus (Thunb.) Nees ex Steud.; Helopus villosus (Thunb.) Nees; Panicum tuberculiflorum Steud.; Paspalum distichum Houtt.; Paspalum villosum Thunb. ex A. Murria; Paspalum villosum Thunb. Panicum gongylodes Jacq.; Panicum hirsutissimum Steud.; Panicum jumentorum Pers.; Panicum laeve Lam.; Panicum maximum Jacq.; Panicum maximum var. gongylodes (Jacq.) Döll; Panicum maximum var. pubiglume K. Schum. ex Peter; Panicum maximum var. pubiglume K. Schum.; Panicum maximum var. trichoglume Robyns; Panicum polygamum Sw.; Panicum polygamum var. gongylodes (Jacq.) E. Fourn.; Panicum praticola Salzm. ex Döll; Panicum scaberrimum Lag.; Panicum trichocondylum Steud.; Urochloa maxima (Jacq.) R.D. Webster; Urochloa maxima var. trichoglumis (Robyns) R.D. Webster Burkart 16298 (SI); Laegaard et Norsangsni 21788 (SI); Otero 238 (SI) Eriochloa procera (Retz.) C.E. Hubb. Eriochloa punctata (L.) Desv. ex Ham. Eriochloa setosa (A. Rich.) Hitchc. Eriochloa villosa (Thunb.) Kunth Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs 123 Angulo et Ridoutt 208 (SI); Kreucker 608 (SI); Laegaard 21748 (SI); Pappi 3890 (SI); Probst 2834 (SI); Ramos 125 (SI) Bernasconi 5614 (SF); D’Angelo 185 (SF); Lewis 651 (SF); Pensiero 5173a, 5214 (SF); Pensiero et Exner 5635, 6211 (SF); Pensiero et Marino 3669, 3727, 3773, 3777 (SF); Pensiero et Tivano 3029 (SF); Pire et Nisensohn 312 (SF); Boelcke 6786, 6794 (SI); Burkart 16169, 17160 (SI); Dusén 13688 (SI); Fortunato et al. 2690 (SI); Guaglianone et al. 269, 432 (SI); Krapovickas et al. 25571 (SI); Morrone et al. 2005 (SI); Muñoz 5464 (SI); Romanczuk et al. 131 (SI); Runyon 717 (SI); Schinini et Martinez Crovetto 12906 (SI); Zuloaga et al. 3294 (SI) Brother 991 (SI) Chase 16782 (SI) Legname et al. 6964 (LIL); Bianchi 1646 (MCNS); Del Castillo 1146 (MCNS); Juarez 1812, 1869 (MCNS); Juarez et Varela 1968 (MCNS); Legname et al. 10140 (MCNS); Novara 3690, 5796, 7698, 7791, 8378,10986, 11430 (MCNS); Palacı́ 724 (MCNS); Tolaba 92 (MCNS);Woodburry et al. W-I108 (NY); Horubeck DW7 (NY); D’Angelo 266 (SF); Pensiero et Kiverling 6304 (SF) Inflorescence diversity and evolution in the PCK Clade (Poaceae) 139 Table 1 continued Species Synonyms Voucher Melinis leucantha (Hochst. ex A. Rich.) Chiov. Melinis minutiflora P. Beauv. Tricholaena teneriffae (L. f.) Link; Tricholaena teneriffae subsp. teneriffae Muhlenbergia braziliensis Steud.; Agrostis glutinosa Fisch. ex Nees; Agrostis glutinosa Fisch. ex Schrank; Agrostis polypogon Salzm. ex Steud.; Melinis maitlandii fo. mutica (Chiov.) Robyns; Melinis maitlandii Stapf & C.E. Hubb.; Melinis minutiflora f. inermis (Döll) Stapf & C.E. Hubb.; Melinis minutiflora f. mutica Chiov.; Melinis minutiflora var. glutinosa (Nees) Kuntze; Melinis minutiflora var. inermis (Döll) Rendle; Melinis minutiflora var. inodora Kuntze; Melinis minutiflora var. mutica Hack.; Melinis minutiflora var. pilosa Staff; Melinis minutiflora var. setigera Clayton; Melinis purpurea Stapf & C.E. Hubb.; Melinis tenuinervis f. mutica Stapf & C.E. Hubb. ex Peter; Melinis tenuinervis Staff; Melinis tenuinervis var. parvispicula C.E. Hubb. ex Peter; Muhlenbergia brasiliensis Steud.; Panicum melinis Trin.; Panicum melinis var. inerme Döll; Panicum minutiflorum (P. Beauv.) Raspail; Suardia picta Schrank; Tristegis glutinosa Nees Panicum monachne Trin.; Tricholaena monachne (Trin.) Stapf & C.E. Hubb. Erianthus repens (Willd.) P. Beauv.; Melinis argentea Mez; Melinis brachyrhynchus Mez; Melinis rosea (Nees) Hack.; Monachyron roseum (Nees) Parl.; Monachyron tonsum (Nees) Parl.; Monachyron villosum Parl.; Panicum braunii Steud.; Panicum roseum (Nees) Steud.; Panicum roseum fo. hirtum Kuntze; Panicum sphacelatum (Benth.) Steud.; Panicum teneriffae var. roseum (Nees) F.M. Bailey; Panicum tonsum (Nees) Steud.; Rhynchelytrum dregeanum Nees; Rhynchelytrum dregeanum var. annuum Chiov.; Rhynchelytrum dregeanum var. intermedium Chiov.; Rhynchelytrum repens (Willd.) C.E. Hubb.; Rhynchelytrum repens var. roseum (Nees) Chiov.; Rhynchelytrum roseum (Nees) Stapf & C.E. Hubb. ex Bews; Rhynchelytrum roseum (Nees) Stapf & C.E. Hubb.; Rhynchelytrum tonsum (Nees) Lanza & Mattei; Rhynchelytrum villosum (Parl.) Chiov.; Saccharum repens Willd.; Saccharum sphacelatum (Benth.) Walp.; Tricholaena dregeana (Nees) T. Durand & Schinz; Tricholaena fragilis A. Braun; Tricholaena repens (Willd.) Hitchc.; Tricholaena repens var. rosea (Nees) Alberts.; Tricholaena rosea Nees; Tricholaena sphacelata Benth.; Tricholaena tonsa Nees; Tricholaena tonsa var. submutica Schweinfurth Ischaemum involutum G. Forst.; Thuarea latifolia R. Br.; Thuarea media R. Br.; Thuarea sarmentosa Pers. Pappi 3884 (LIL) Melinis monachne (Trin.) Pilg. Melinis repens (Willd.) Zizka Thuarea involuta (G. Forst.) R. Br. ex Sm. Andersson 9776 (LIL); Barkley et al. 1542 (LIL); Bro. Apolinar 688 (LIL); Castellanos 1435, 5767 (LIL); Dusén 17050; Gonzalez 64666 (LIL); Hunziker 2573 (LIL); Irwin et al. s/n (LIL); Klevens et Barkley 17C353 (LIL); Leojnoldo 18 (LIL); Lufantes 1228 (b) (LIL); Pabst 20 (LIL); Palacios et al. 3309 (LIL); Rambo 42026, 43557 (LIL); Ruit C-1130 (LIL); Schulz 12258 (LIL); Schunke 8171(LIL); Stürpe 617 (LIL); Barbosa 664 (SI) Godfrey et Meeuse SH-1596 (US); Gossweilerii 10627 (US); Smook 7067 (US) Smook 9270 (LIL); Dalla Fontana s/n (SF); Morrone et Pensiero 222, 378, 436 (SF); Pensiero 4093 (SF); Tivano 513 (SF); Vegetti 1123 (SF); Alonso 970 (SI); Bogdon 4562 (SI); Romanczuk et al. 426 (SI) Edaño 56725 (US); Smith 9508 (US); Williams 220 (US) 123 140 R. Reinheimer, A. C. Vegetti Table 1 continued Species Synonyms Voucher Urochloa acuminata (Renvoize) Morrone and Zuloaga Brachiaria tatianae Zuloaga and Soderstr.; Panicum megastachyum Nees; Streptostachys acuminata Renvoize Brachiaria adspersa (Trin.) Parodi; Brachiaria adspersa (Trin.) S.T. Blake; Brachiaria echinulata (Mez) L.R. Parodi; Panicum adspersum Trin.; Panicum adspersum var. exile Lindm.; Panicum adspersum var. neesi Lindm.; Panicum echinulatum Mez; Panicum echinulatum var. boliviense Henrard; Panicum keyense Mez; Panicum thomasianum Steud. ex Döll Zuloaga et al. 4766, 4843 (SI) Urochloa adspersa (Trin.) R.D. Webster Urochloa advena (Vickery) R.D. Webster Urochloa arrecta (Hack. Ex T. Durand and Schinz) Morrone and Zuloaga. Urochloa atrisola R.D. Webster Urochloa bovonei (Chiov.) A.M. Torres and C.M. Morton Urochloa brachyura (Hack. ex Schinz) Stapf Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster Urochloa ciliatissima (Buckley) R.D. Webster Urochloa comata (Hochst. ex A. Rich.) Stapf Urochloa decidua Morrone and Zuloaga Urochloa decumbens (Stapf) R.D. Webster 123 Brachiaria advena Vickery Parodi 14594 (BAA); Rua et al. 22994 (BAA); Saravia Toledo 283 (BAA); Venturi 1587 (BAA); Krapovickas et Schinini 30505 (CTES);Schulz?? 3869 (CTES) (MCNS); Ahumada et al. 9379, 9383 (JUA); Cabrera et al. 23323 (LIL); Legname et Cuezo 8193 (LIL); Norrman et al. 192 (LIL); Saravia Toledo et Parada 17 (MCNS); Britton et Shaper 334 (NY); Hansen 2473 (NY); Luna 981 (NY); Nee 44580, 44835 (NY); Pierotti 201 (NY); Tonell 2630 (NY); Pensiero et al. 5053 (SF); 13466 (SI); Ahumada 4464 (SI); Alonso 6 (SI); Burkart 20144, 20200, 20378 (SI); Burkart et Troncoso 11442 (SI); Cabrera et al. 26408, 26479, 27477, 31440, 34016 (SI); Guaglianone et al. 612 (SI); Job 13463 (SI); Krapovickas et Schinini 30779 (SI); Lewis et Pire 800 (SI); Pire 1343 (SI); Schinini et Bordas 15141 (SI); Schinini et Mroginski 4602 (SI); Schulz 3329 (SI); Stofella 107 (SI); Stuckert 12792 (SI); Zuloaga et al. 2989 (SI); Zuloaga et Deginani 3703 (SI); Zuloaga et Morrone 3031, 3049, 3050, 3056 (SI) Killick 4541 (MO) Brachiaria arrecta (Hack. ex T. Durand and Schinz) Stent; Brachiaria radicans Napper; Panicum arrectum Hack. ex T. Durand and Schinz Brachiaria atrisola (R.D. Webster) B.K. Simon Brachiaria viridula Stapf; Brachiaria bovonei (Chiov.) Robyns; Brachiaria hians Stapf; Panicum bovonei Chiov. Panicum brachyurum Hack. ex Schinz; Urochloa geniculata C.E. Hubb; Urochloa novemnervia C.E. Hubb; Urochloa novemnervia C.E. Hubb. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf; Panicum brizanthum Hochst. ex A. Rich.; Urochloa decumbens (Stapf) R.D. Webster Brachiaria ciliatissima (Buckley) Chase; Panicum ciliatissimum Buckley Brachiaria epaleata Stapf; Brachiaria kotschyana (Hochst. ex Steud.) Stapf; Brachiaria secernenda (Hochst. ex Mez) Henrard; Panicum comatum Hochst. ex A. Rich. _ López 64 (CTES); Borgo et al. 447 (NY); Zuloaga et al. 5618 (NY) Brachiaria decumbens Stapf Honfi 73 (CTES); Cirón et al. 3427 (NY); Davidse et Gonzáles 21954 (NY); Filgueiras 441 (NY); Heringer et al. 1756, 5063 (NY); Nee 45181, 45182, 45992, 46063, 46392, 47388, 47415, 47451, 47853, (NY); Nee et Sundue 51915 (NY); Morrone et Pensiero 117, 315, 371, 497 (SF) Blake 17776 (MO) Maas Greesteranus 4925 (MO); Wiehe 391 (MO) Jahogens 6702 (US); Mott 918 (NY); Moss et Ottley 3480 (NY); Seiner 462 (US); Volk 6696 (NY) Bhorai Kalloo et Centeno 6 (NY); Heringer et al. 2077 (NY); Mori et al. 10560 (NY); Plowman et al. 8695 (NY); Smith et al. 15775 (NY); Morrone et Pensiero 366 (SF) Brant et al. 2222 (MO); Correll et Johnston 18116 (MO) Thomas 4343 (LIL) (US); Hitchcock 24974 (US); Mearns 3044, 3046 (US); Shantz 921 (US); Snowden 1202 (US) Zuloaga 6942 (SI) Inflorescence diversity and evolution in the PCK Clade (Poaceae) 141 Table 1 continued Species Synonyms Voucher Urochloa deflexa (Schumach.) H. Scholz Brachiaria regularis (Nees) Stapf; Brachiaria deflexa (Schumach.) C.E. Hubb. ex Robyns; Panicum deflexum Schumach. Brachiaria dictyoneura (Fig. and De Not.) Stapf; Brachiaria dictyoneura subsp. dictyoneura; Brachiaria humidicola (Rendle) Schweick.; Panicum dictyoneurum Fig. and De Not.; Panicum humidicolum Rendle; Urochloa humidicola (Rendle) Morrone and Zuloaga Brachiaria subquadripara (Trin.) Hitchc.; Brachiaria miliiformis (J. Presl) Chase; Brachiaria distachya (L.) Stapf; Digitaria distachya (L.) Pers.; Panicum distachyon L.; Panicum miliiforme J. Presl; Panicum subquadriparum Trin.; Urochloa subquadripara (Trin.) R.D. Webster Brachiaria dura Stapf Meinzingen et Conert 336, 599, 755, 796 (LIL); De Leeuw 1088 (US); Godfrey H-1731 (US); Schinker 1653 (US);Thorold CB-28, sws/28 (US) Hitchcock 24816 (US); Greenway 10115 (US); Snowden 1219 (US) Urochloa dictyoneura (Fig. and De Not.) Veldkamp Urochloa distachya (L.) T.Q. Nguyen Urochloa dura (Stapf) A.M. Torres and C.M. Morton Urochloa echinolaenoides Stapf Urochloa eminii (Mez) Davidse Urochloa foliosa (R. Br.) R.D. Webster Urochloa fusca (Sw.) B.F. Hansen and Wunderlin Urochloa fusiformis (Reeder) Veldkamp Urochloa gilesii (Benth.) Hughes _ Brachiaria eminii (Mez) Robyns; Panicum eminii Mez. Brachiaria foliosa (R. Br.) Hughes; Panicum foliosum R. Br. Brachiaria fasciculata (Sw.) Parodi; Brachiaria fasciculata (Sw.) S.T. Blake; Brachiaria fasciculata var. carthaginense (Sw.) Beetle; Brachiaria fasciculata var. fasciculata; Brachiaria fasciculata var. reticulata (Torr.) Beetle; Brachiaria fasciculata var. reticulata (Torr.) Vickery; Brachiaria fasciculata var. stricta (Döll) Beetle; Panicum carthaginense Sw.; Panicum chartaginense Sw.; Panicum fasciculatum Sw.; Panicum fasciculatum var. chartaginense (Sw.) Döll; Panicum fasciculatum var. flavescens (Sw.) Döll; Panicum fasciculatum var. fuscum (Sw.) Döll; Panicum fasciculatum var. genuinum Döll; Panicum fasciculatum var. reticulatum (Torr.) Beal; Panicum fasciculatum var. strictum Döll; Panicum fastigiatum Poir.; Panicum flavescens Sw.; Panicum fuscatum J. Presl ex Nees; Panicum fusco-rubens Lam.; Panicum fuscum Sw.; Panicum fuscum var. fasciculatum (Sw.) Griseb.; Panicum fuscum var. fuscum; Panicum fuscum var. reticulatum (Torr.) Scribn. and Merr.; Panicum illinoniense Desv.; Panicum nigrica Willd. ex Spreng.; Urochloa fasciculata Kunth Brachiaria fusiformis Reeder; Brachiaria fusiformis var. pilicoronata (Ohwi) Jansen; Brachiaria villosa var. pilicoronata Ohwi Brachiaria gilesii (Benth.) Chase; Panicum gilesii Benth. Andersson s/n (LIL); Adams 13975, 14313, 14700 (NY); Fosberg 24795 (NY); Fosberg et Stoddart 54884 (NY) Mitchell 12/62 (US); Verboom 1319 (US) Shauty 586 (US) Stuhlmann 3842 (US) Collins 46642 (MO); Snow et Simon 7332 (MO); Blake 20087 (US) Agostini et al. 1848 (NY); Ahumada et al. 9375 (JUA); Breteler 3998; Buting 5399, 5669, 7598, 7664, 9398 (NY); Byron et Smarino 20981 (NY); Burkart 16991, 20370 (SI); Curtiss 748 (SI);Eiten et Eiten 10315, 10439 (NY); Garber 36 (NY); Holm-Nielsen et al. 2020, 2482 (NY); Krapovickas et Schinini 30945 (CTES); Krapovickas 1544 (LIL, SI); Lieser et González 12154 (NY); Molina 24272 (BAA); Santa Cruz 3500 (BAA); Small 10515 (NY); Stuckert 21603; West s/n (NY) Ramos 8214 (US); Ramos et Edaño 44646 (US); Williams 1963 (US) Hubbard 6011, 7051 (MO) 123 142 R. Reinheimer, A. C. Vegetti Table 1 continued Species Synonyms Voucher Urochloa glumaris (Trin.) Veldkamp Brachiaria ambigua (Trin.) A. Camus; Brachiaria paspaloides (J. Presl) C.E. Hubb.; Panicum ambiguum Trin.; Panicum glumare Trin.; Panicum urochloa Steud.; Urochloa ambigua (Trin.) Pilg.; Urochloa glabra Brongn.; Urochloa paspaloides J. Presl Urochloa holosericea (R. Br.) R.D. Webster Urochloa humidicola (Rendle) Morrone and Zuloaga Brachiaria holosericea (R. Br.) Hughes; Panicum holosericeum R. Br. Brachiaria dyctioneura Stapf; Brachiaria dictyoneura subsp. humidicola (Rendle) Catasús, Brachiaria rautanenii (Hack.) Stapf; Panicum humidicolum Rendle; Urochloa dictyoneura (Fig. and De Not.) Veldkamp Brachiaria jubata (Fig. and De Not.) Stapf; Panicum jubatum Fig. and De Not. Brachiaria kurzii (Hook. f.) A. Camus; Brachiaria lanceata Ohwi; Brachiaria lanceata var. timorensis (Ohwi) Jansen; Brachiaria timorensis Ohwi; Panicum kurzii Hook. f.; Urochloa kurzii (Hook. f.) R.D. Webster Brachiaria lachnantha (Hochst.) Stapf; Panicum lachnanthum Hochst.; Panicum lachnanthum Torr. Brachiaria lata (Schumach.) C.E. Hubb.; Panicum amplexifolium Hochst.; Panicum hamadense Mez; Panicum insculptum Steud.; Panicum latum Schumach.; Urochloa insculpta (Steud.) Stapf Brachiaria leucacrantha (K. Schum.) Stapf; Panicum leucacranthum K. Schum. Brachiaria lorentziana (Mez) Parodi; Panicum lorentzianum Mez; Panicum velutinosum f. violascens Stuck.; Panicum velutinosum f. viride Stuck. Clayton 5073 (US); Evans 629 (NY); Gould 13445 (US); Gould et Cooray 13733 (US); Hosaka 3143 (NY); Hürlimann 551, 620 (NY); Kajewski 279 (NY); Main et Aden 1563 (US); Procten 4526 (NY); Samlumgen von Otto Kuntze’s Weltreise 75 (NY); St. John 16681 (NY); Taylor P-2788-E; Vera Santos 4489, 5018 (US); Wray 334 (NY); Yunker 9114, 9486, 15414, 15820 (NY) Brass 5910, 7810 (US) Urochloa jubata (Fig. and De Not.) Sosef Urochloa kurzii (Hook. f.) T.Q. Nguyen Urochloa lachnantha (Hochst.) A.M. Torres and C.M. Morton Urochloa lata (Schumach.) C.E. Hubb. Urochloa leucacrantha (K. Schum.) Stapf Urochloa lorentziana (Mez) Morrone and Zuloaga Urochloa meziana (Hitchc.) Morrone and Zuloaga Brachiaria meziana Hitchc Urochloa mollis (Sw.) Morrone and Zuloaga Brachiaria mollis (Sw.) Parodi; Panicum didistichum Mez; Panicum molle Griseb.; Panicum molle Sw.; Panicum moritzii Mez; Panicum polytrichum Mez; Panicum velutinosum Nees ex Trin.; Panicum velutinosum Nees 123 Ballèe 3503 (NY); Bhorai Kalloo et Centeno 5 (NY); Nee 46051 (NY) Pilz 2061 (LIL); Meinzinger et Conert 352, 556, 816 (LIL) Monod de Froideville 1448 (US) 16212 (CIAT) 26886 (CIAT) 16546 (CIAT); Schlieben 6488 (LIL) Nicora 7108 (BAA); Parodi 14600 (BAA); Saravia Toledo 252 (BAA); Saravia Toledo 1522 (CTES); Schulz 1683 (CTES); Jaime 8 (LIL); Zuloaga et Deginani 310 (LIL); Navarro 174 (MCNS); Maruña et al. 598 (NY); Stuckert 18759a (NY); 25398 (SI); Ahumada et Castellon 4763, 4781 (SI); Burkart 12263 (SI); Burkart et al. 25246 (SI); Burkart et Troncoso 11482, 11992 (SI); Cabrera et al. 30236, 30606 (SI); Cuellar 3 (SI); Esteban 10682 (SI); Marquez 16 (SI); Nicora 1910, 17531, 18472 (SI); Nicora et al. 9020 (SI) (SF); Perez 210 (SI); Schulz 3250, 17828 (SI); Stuckert 366, 11070 (SI); Ulibarri 335, 358 (SI); Venturi 1676 (SI); Zuloaga et al. 2678 (SI); Zuloaga et Deginani 3496 (SI); Zuloaga et Morrone 3051 (SI) Davidse 9928 (LIL); Fisher 35224 (LIL); Hitchcok 402 (LIL); Davidse et Davidse 9928 (MO); Kral 27444 (MO) Alain et al. 34441 (NY); Bunting 7963, 8214 (NY); Madsen 63390 (NY); Weberbauer 7714 (NY) Inflorescence diversity and evolution in the PCK Clade (Poaceae) 143 Table 1 continued Species Synonyms Voucher Urochloa mosambicensis (Hack.) Dandy Echinochloa notabilis (Hook. f.) Rhind; Panicum mosambicense Hack.; Panicum notabile Hook. f.; Urochloa pullulans Stapf; Urochloa pullulans var. mosambicensis (Hack.) Stapf; Urochloa rhodesiensis Stent Brachiaria glabrinodis (Hack.) Henrard; Brachiaria mutica (Forssk.) Stapf; Brachiaria numidiana (Lam.) Henrard; Brachiaria purpurascens (Raddi) Henrard; Panicum amphibium Steud.; Panicum barbinode Trin.; Panicum equinum Salzm. ex Steud.; Panicum glabrinode Hack.; Panicum guadaloupense Spreng. ex Steud.; Panicum muticum Forssk.; Panicum numidianum Lam.; Panicum paraguayense Steud. ex Döll; Panicum pictigluma Steud.; Panicum purpurascens Raddi; Paspalum glabrinode (Hack.) Morrone and Zuloaga; Urochloa mutica (Forssk.) R.D. Webster ex Zon Brachiaria nigropedata (Munro ex Ficalho and Hiern) Stapf; Brachiaria melanotyla (Hack.) Henrard; Panicum melanotylum Hack.; Panicum nigropedatum Munro ex Ficalho and Hiern Brachiaria notochthona (Domin) Stapf; Brachiaria gilesii (Benth.) Chase; Urochloa gilesii (Benth.) Hughes; Panicum notochthonum Domin; Urochloa gilesii subsp. gilesii. Brachiaria oblita (Swallen) Tovar; Panicum oblitum Swallen Brachiaria bulawayensis (Hack.) Henrard; Eriochloa bolbodes (Hochst. ex Steud.) Schweinf.; Helopus bolbodes Hochst. ex Steud.; Panicum bolbodes (Hochst. ex Steud.) Asch. and Schweinf.; Panicum bulawayense Hack.; Panicum oligotrichum Fig. and De Not.; Urochloa bolbodes (Hochst. ex Steud.) Stapf; Urochloa bolbodes (Steudel) Stapf Brachiaria ophryodes Chase Banda et Kananji 3822 (NY); Liogier et Martorell 34441 (NY); Pensiero et Marino 4446 (NY); Sinclair 26 (NY) Panicum borzianum Mattei; Panicum controversum Steud.; Panicum helopus f. glabrescens K. Schum.; Panicum helopus Trin.; Panicum helopus var. glabrescens (K. Schum.) Stapf; Panicum hochstetterianum A. Rich.; Panicum oxycephalum Peter; Panicum panicoides (P. Beauv.) Hitchc.; Panicum setarioides Peter; Panicum trichopus subsp. breviglume Chiov.; Panicum trichopus var. glaberrimum Chiov.; Panicum trichopus var. trichophorum Chiov.; Panicum urochloa Desv.; Setaria pilifera Spreng.; Urochloa helopus (Trin.) Stapf; Urochloa helopus var. hochstetteriana (A. Rich.) Chiov.; Urochloa panicoides var. pubescens (Kunth) Bor; Urochloa pubescens Kunth; Urochloa ruschii Pilg. Krapovickas et al. 27906 (CTES); Vanni et al. 4166 (CTES); Ahumada et al. 9376, 9382 (JUA); Ahumada 5166 (MCNS); Del Castillo 269, 588, 599 (MCNS); Del Castillo et al. 475 (MCNS); Del Castillo et Neuman 374 (MCNS); Falce s/n (MCNS); Nicora et al. 9016 (MCNS) (SF); Novara et al. 682, 710, 728 (MCNS); Novara et Bruno 8798 (MCNS); Saravia Toledo 849 (MCNS); Bates 20671 (NY); Johnson 707 (NY); Pinkava 14365 (NY); Sinclair 25 (NY); Smith 3041 (NY); Ahumada 4709 (SI); Ahumada et Castellon 5021 (SI); Cabrera et al. 26171, 31886 (SI); Deginani et Cialdella 233 (SI); Garcia et Grenni 524 (SI); Novara 3348 (SI); Vignale et Breglia 176 (SI); Volk 6500 (NY); Zuloaga et Morrone 3032, 3036, 3052 (SI) Urochloa mutica (Forssk.) T.Q. Nguyen Urochloa nigropedata (Munro ex Ficalho & Hiern) Stapf Urochloa notochthena (Domin) Hughes Urochloa oblita (Swallen) Morrone and Zuloaga Urochloa oligotricha (Fig. and De Not.) Henrard Urochloa ophryodes (Chase) Morrone and Zuloaga Urochloa panicoides P. Beauv. Bartlett 20315 (BAA); Hirschhorn 7356 (BAA); Parodi 14790 (BAA); Carnevali 1180 (CTES); Quarı́n 2387 (CTES); Asplund 19241 (NY); Degener 11501 (NY); Duke 9728 (NY); Hekking 945 (NY); Herrera 461 (NY); Hoock-Cayenne 196 (NY); Kazuto 10594, 10728 (NY); Lee and Weller 119 (NY); McDaniel et Rimachi 23369 (NY); Rimachi 5913 (NY); Steyermark et al. 121232 (NY); Yuncker T.G. 9659 (NY) Bogdan 5144 (US); Burtt 1285 (US); Liebenberg 4505 (US) Hourigan 21 (US) Holm-Nielsen et al. 4926 (MO); Peterson et al. 8909 (MO) Liebenberg 11 (US); Pappi 274 (US); Robinson 1425 (US); Shantz 475 (US) Hitchcock 401 (LIL) 123 144 R. Reinheimer, A. C. Vegetti Table 1 continued Species Synonyms Voucher Urochloa paucispicata (Morong) Morrone and Zuloaga Acroceras paucispicatum (Morong) Henrard; Brachiaria paucispicata (Morong) Clayton; Panicum paucispicatum Morong Urochloa piligera (F. Muell. ex Benth.) R.D. Webster Brachiaria piligera (F. Muell. ex Benth.) Hughes; Brachiaria piligera var. intercedens (Domin) Hughes; Brachiaria subquadripara var. piligera (F. Muell. ex Benth.) Reeder; Panicum intercedens Domin; Panicum piligerum F. Muell. ex Benth. Brachiaria plantaginea (Link) Hitchc.; Panicum disciferum E. Fourn.; Panicum distans Salzm. ex Döll; Panicum distans Salzm. ex Steud.; Panicum leandri Trin.; Panicum plantagineum Link; Urochloa discifera (E. Fourn.) Morrone and Zuloaga Quarı́n 94 (CTES); Saravia Toledo 1523 (CTES); Cuezzo et al. 4486 (LIL); Nee 42287 (LIL); Falce HG1145 (MCNS); Karlsson 20 (MCNS); Novara 10121 (MCNS); Ragonese 2539 (SF); Ahumada 4466 (SI); Cantino 735 (SI); Hauman s/n (SI); Ibarrola 225 (SI); Insfrán 1030 (SI); Nicora 18427 (SI) Carr 11398 (MO); Hubbard et Winders 6345 (MO); Lazarides 4168 (MO) Urochloa plantaginea (Link) R.D. Webster Urochloa platynota (K. Schum.) Pilg. Urochloa platyphylla (Munro ex C. Wright) R.D. Webster Urochloa bifalcigera (Stapf) Stapf; B. platynota (K. Schum.) Robyns Brachiaria extensa Chase; Brachiaria platyphylla (Munro ex C. Wright) Nash; Panicum platyphyllum Munro ex C. Wright; Paspalum platyphyllum Griseb.; Urochloa extensa (Chase) C. Nelson and Fern. Casas; Urochloa platyphylla (Griseb.) R.D. Webster Urochloa platytaenia (Stapf) Crins Brachiaria platytaenia Stapf; Brachiaria oligobrachiata (Pilg.) Henrard Kartesz; Panicum oligobrachiatum Pilg.; Urochloa oligobrachiata (Pilg.) Brachiaria praetervisa (Domin) C.E. Hubb.; Brachiaria windersii C.E. Hubb.; Panicum kochii Mez; Panicum praetervisum Domin Brachiaria holotricha Ohwi; Brachiaria pubigera (Roem. and Schult.) S.T. Blake; Brachiaria ramosa var. grandiflora Hughes Urochloa praetervisa (Domin) Hughes Urochloa pubigera (Roem. and Schult.) R.D. Webster 123 MacDonald 12465; Dusén 14761 (BAA); Parodi 6422 (BAA); Ahumada 4142 (CTES); Schulz 11052 (CTES); Ahumada et al. 9374, 9378, 9385 (JUA); Türpe 3055 (LIL); Morrone et Pensiero 358 (SF); Nicora et al. 9018 (SF); Ragonese 2128 (SF) (BAA); Ahumada et Rotman 4397 (SI); Cabrera et al. 26152, 26414, 30176, 30262, 34694 (SI); Deginani et Cialdella 16 (SI); Guaglianone et al. 1983 (SI); Zuloaga et al. 1466, 2889 (SI); Zuloaga et Morrone 3005, 3014, 3016, 3018, 3030 (SI) Lab Stapf 1926 (US); Lienberg May 1930 (US); Snowden 1222 (US) Bartlett 20299 (BAA); Lewis et Collantes 139 (BAA); Quarin 648 (BAA); Rosengurt B4898 (BAA); Ahumada 1506, 1642 (CTES); Lazarte s/ n (LIL); Del Castillo et Varela 42 (MCNS); Banks D.J. 2571 (NY); Galvan et al. 27 (NY); Halse 6125 (NY); Hunziker 13808 (NY); Rojas 12644 (NY); Venturi 2384 (NY); Brollo 238 (SF); Brollo et Tivano 604 (SF); D’Angelo 149 (SF); Pensiero 135, 141, 833, 1957, 5213 (SF); Pensiero et al. 1443, 5151 (SF); Pensiero et Kiverling 6382 (SF); Pensiero et Marino 3561 (SF); Pensiero et Tivano 2964, 3032 (SF); Ragonese 2284, 3198 (SF); 25560 (SI); Ahumada 615 (SI); Bartlett 19718, 19719 (SI); Bissio 832 (SI); Burkart 12759 (SI); Burkart et Bacigalupo 21028 (SI); Cabrera et al. 26492 (SI); Gomez 187 (SI); Job 755 (SI); Lewis 1492 (SI); Meyer 388 (SI); Nicolini 20767 (SI); Parodi 563a (SI); Pedersen 4671 (SI); Quarin et al. 2007 (SI); Scipione 268 (SI); Venturi 2384, 7526 (SI); Zuloaga et al. 2694, 2991, 3346 (SI); Zuloaga et Deginani 3668 (SI) Leleum 983 (US); Shauty 5941/2; Verboon 1193 (US) Badman 5230 (NY) Begnin 198 (US) Inflorescence diversity and evolution in the PCK Clade (Poaceae) 145 Table 1 continued Species Synonyms Voucher Urochloa ramosa (L.) T.Q. Nguyen Brachiaria ramosa (L.) Stapf; Brachiaria reptans (L.) C.A. Gardner and C.E. Hubb.; Echinochloa ramosa (L.) Roberty; Panicum helopus var. glabrior Benth; Panicum pubescens R. Br.; Panicum pubigerum Roem. and Schult.; Panicum ramosa L.; Panicum ramosum L.; Urochloa reptans (L.) Stapf Panicum holtzii Peter; Urochloa gorinii Chiov. Brachiaria decumbens var. ruziziensis (R. Germ. and Evrard) Ndab.; Brachiaria ruziziensis R. Germ. and Evrard; Urochloa ruziziensis (R. Germ. and Evrard) Morrone and Zuloaga Urochloa sclerochlaena var. commelinoides Chiov. Brachiaria setigera (Retz.) C.E. Hubb.; Panicum euryphyllum Peter; Panicum setigerum Retz.; Panicum trichopodioides Mez and Schum.; Urochloa trichopodioides (Mez and Schum.) S.M. Phillips and S.L. Chen Brachiaria subulifolia (Mez) Clayton; Brachiaria filifolia Stapf; Panicum subulifolium Mez Brachiaria texana (Buckley) S.T. Blake; Panicum texanum Buckley; Panicum texanum Vasey Eriochloa trichopus (Hochst.) Benth.; Eriochloa trichopus var. glabrata Schweinf.; Helopus trichopus (Hochst.) Steud.; Panicum papillosum Fenzl ex Steud.; Panicum trichopodon A. Rich.; Panicum trichopus Hochst.; Panicum trichopus var. chiovendae Mattei; Urochloa brachyphylla Gilli; Urochloa engleri Pilg. Panicum venosum Swallen Brown et Brown 98 (US); Brittom et al. 476; Buting 7694 (NY); Hitchcock 16605 (NY); Hoock 753, 754 (NY); Jemman 6024 (NY); Faulkner 3769 (US); Michelnome 4-9-30 (US); William 3479 (US) Urochloa rudis Stapf Urochloa ruziziensis (R. Germ. and Evrard) Crins Urochloa sclerochlaena Chiov. ex Chiarugi Urochloa setigera (Retz.) Stapf Urochloa subulifolia (Mez) A.M. Torres and C.M. Morton Urochloa texana (Buckley) R.D. Webster Urochloa trichopus (Hochst.) Stapf Urochloa venosa (Swallen) Morrone and Zuloaga Urochloa villosa (Lam.) T.Q. Nguyen Urochloa whiteana (Domin) R.D. Webster Urochloa xantholeuca (Hack. ex Schinz) H. Scholz Yvesia madagascariensis A. Camus Brachiaria distichophylla (Trin.) Stapf; Brachiaria villosa (Lam.) A. Camus; Brachiaria coccosperma (Steud.) Stapf ex Reeder; Brachiaria villosa f. glabriglumis (Ohwi) Ohwi; Brachiaria villosa var. glaberrima Basappa and Muniy.; Brachiaria villosa var. glabrata S.L. Chen and Y.X. Jin; Panicum coccospermum Steud.; Panicum villosum Lam.; Urochloa coccosperma (Steud.) Stapf ex Reeder Brachiaria whiteana (Domin) C.E. Hubb.; Panicum whiteanum Domin Brachiaria xantholeuca (Hack. ex Schinz) Stapf; Panicum xantholeucum Hack. ex Schinz _ Wingfield 3145 (US) 654 (CIAT); Ramos s/n (SF); Reinheimer et al. 8 (SF); Reinheimer et Guarise 105 (SF) Graham 83 (US) Davidse et Sumithraarachchi 8996 (NY); MuellerDombois et Cooray 67121011 (US); MilneRedhead et Taylor 7270 (US); Faulkner 3293 (US); Gould et Cooray 13712 (US); Kabuye et al. TPR-50 (US) H.B.G. 27322 (LIL); Laegaard 15786 (US); MilneRedheard et Taylor 8034 (US) Bryson et Wayne Morris 6906 (MO); Richard II 1352 (MO); Thomas 146055 (MO); Coston 61 (NY) Ash 2564 (US); Madsen s/n (NY); Swaziland 15251 (US) Leavenworth 481 (MO) Beale 2168 (LIL); Meinzingen and Conert 55, 402, 438, 468, 616 (LIL); Praia Varela 2285 (MO); Sihvonen 247 (MO); Clemens 16216 (NY); Ramos 80569 (NY); Adjanohoum 385A (US; MO); Haperup O. 413 (US); Hitchcock 24936 (US); Maitland 892A (US); Pobeguin 1734 (US) Hubbard 2749, 8092 (MO) Burlt 4553 (US); Dyson-Hudson 56 (US); Liebenberg 9 (US); Williams 238 (US) Bathie 11055 (US); Perroi 11055 (US) CIAT Centro Internacional de Agricultura Tropical; CTES Herbario del Instituto de Botánica del Nordeste; ISC Ada Hayden Herbarium; LIL Herbario Fanerogámico de la Fundación Miguel Lillo; MCNS Herbario del Museo de Ciencias Naturales de Salta; MO Missouri Botanical Garden; NY New York Botanical Garden; SF Herbario ‘‘E. A. Ragonese’’; BAA Herbario ‘‘Gaspar Xuarez’’; SI Herbario del Instituto de Botánica ‘‘Darwinion’’; US Smithsonian Institution 123 146 included because of lack of material. The botanical nomenclature for the species of the PCK Clade is highly diverse and confuse. For that reason, in Table 1 we also provided the most common synonyms for each species. We studied the branch system of the entire plant using the terminology proposed by Troll and Weberling (Troll 1964; Weberling 1989; Vegetti and Weberling 1996; Rua and Weberling 1998) based on the comparison of plant forms (Rua 1999). Observations were recorded according to the different zones of the synflorescence (shoot system of the plant originated from the apical meristem or axillary buds, (innovations), Troll and Weberling 1989) and schematic drawings have been made accompanying the descriptions. The figures have been prepared with the intention to reflect as closely as possible the shape and architecture of the inflorescence as seen in nature or herbarium material. For SEM observations, inflorescences were collected from plants of Megathyrsus maximus (Reinheimer 129, SF) and Urochloa lata (Schumach.) C.E. Hubb. (CIAT # 26886) growing at the Agronomy School of the University of Litoral (Esperanza, Argentina), after which they were fixed in FAA (formalin:acetic acid:70% ethanol, 10:5:85, v/v), and dehydrated in an alcohol series plus two final changes of 100% acetone. Dehydrated material was critical point dried using CO2 as transitional fluid and coated with gold–palladium using a Thermo VG Scientific POLARON SC7620 SPUTTER COATER (Balzers, Switzerland). All samples were observed and photographed using a PHILIPS XL30 series (Eindhoven, The Netherlands) scanning electron microscope from the Electron Microscopy Service of the ‘‘Bernardino Rivadavia’’ Natural Science Museum (Buenos Aires, Argentina). Results Synflorescence zones In the PCK Clade, the main inflorescence axis of the plant and each innovation can be considered as a synflorescence of a different degree. Each synflorescence has a distal region, the anthotagma (region that bears the floral axis) and a proximal region, the trophotagma (region that usually has a vegetative function) (Figs. 2–4). In all genera analyzed in this work, the anthotagma region is represented by the terminal inflorescence (IF) which develops above the last formed leaf along the main axis or innovation. In the PCK Clade the inflorescence is a paniculodium, that is, a panicle that has spikelets in place of flowers. In general, the inflorescence has flowering branches (paracladia or branches of the inflorescence, B) which lack well developed leaves or bracts, except for those that form the spikelet (Figs. 2–4). 123 R. Reinheimer, A. C. Vegetti Fig. 2 Brachiaria eruciformis synflorescence (shoot system originated from the apical meristem or axillary buds of the whole plant). a simplified scheme; b photograph of the synflorescence. HZ inhibition zone; IZ innovation zone; TT trophotagma region; IF inflorescence. The arrow indicates the terminal spikelet on the main florescence In the PCK Clade, the inflorescence begins with the most proximal primary branch (B1) and extends to the most distal primary branch. Distal to the uppermost primary branch, the main axis of the inflorescence continues its development and, depending on the species, ends in a main florescence or terminal spikelet (TS), or aborts (Figs. 2–4). The trophotagma region (TT) is the region of the synflorescence that bears well-developed leaves, sometimes preceded by proximal cataphylls (Figs. 2–4). Usually, the trophotagma region shows a proximal area of short internodes (the innovation zone, IZ) where the innovation axis (IN) originates from axillary buds, and a distal area of long internodes, that could be the inhibition zone (HZ) or may also behave partially as an enrichment zone (EZ). Presence of an enrichment zone in the trophotagma region Among the studied species, the area of long internodes in the trophotagma region commonly shows an enrichment zone and an inhibition zone. That is, the axillary buds of the most distal vegetative leaves of the trophotagma region (just below the inflorescence), often develop branches that bear well developed leaves (paracladia of the trophotagma or branches of the trophotagma, BTT) and eventually may end in a terminal inflorescence (Fig. 4). In these cases, the enrichment zone of the trophotagma region is represented by branches of the trophotagma that repeat the ramification Inflorescence diversity and evolution in the PCK Clade (Poaceae) 147 Fig. 3 Simplified scheme of the Urochloa synflorescence without branches of the trophotagma. a Urochloa paucispicata; b Urochloa brizantha. HZ inhibition zone; IN innovation; IN(SinFII) synflorescence of second order; IZ innovation zone; lgB1 long primary branch; TT trophotagma region; IF inflorescence. The arrow indicates the terminal spikelet of the main axis. The asterisk indicates the absence of the terminal spikelet on the main axis pattern of the main axis. In Brachiaria, Chaetium, Eriochloa, Megathyrsus, Melinis, and Urochloa the enrichment zone in the trophotagma region may be present or not depending on the studied species. In contrast, synflorescences of Thuarea and Yvesia never develop an enrichment zone in the long internode region (Table 2). Variation of the inflorescence The inflorescence is the most variable region of the synflorescence among the studied species. Morphological differences include: (1) presence or absence of a bract entirely surrounding the inflorescence; (2) different degrees of homogenization of the primary branches (morphological similarity of inflorescence branches); (3) presence or absence (truncation) of the distal part of the main axis and distal parts of the branches; (4) orientation of primary branches along the main axis (inflorescence symmetry); (5) number and maximum branch degree of the primary branches; (6) differences in main axis internode length and disposition of the primary branches; (7) differences in the internode length of branches; (8) spikelet distribution and organization on the branch; and (9) total number, ramification degree and phyllotaxis of the most distal primary branch of the inflorescence. Presence of foliage leaves in the inflorescence Thuarea involuta (G. Forst.) R. Br. ex Sm. is the only species that has a spathaceous bract that encloses and presumably 123 148 R. Reinheimer, A. C. Vegetti Fig. 4 Synflorescence of Urochloa leucacrantha with branches of the trophotagma. a simplified scheme; b photograph of the synflorescence. BTT trophotagma branch; EZ enrichment zone; HZ inhibition zone; IN innovation; IN(SinFII) synflorescence of second order; IZ innovation zone; lgB1 long primary branch; TT trophotagma region; IF inflorescence. The arrow indicates the terminal spikelet on the main florescence protects the inflorescence. This bract subtends the single primary branch that makes up the inflorescence (Fig. 8a). Homogenization degree of the inflorescence We found three different homogenization degrees among the inflorescences of the PCK Clade: (1) fully homogenized, (2) partially homogenized, and (3) non-homogenized. In the fully homogenized inflorescence, the maximum degree of ramification (in general, second or third order; B2, B3) is the same along the branch and for all primary branches, independent of position on the inflorescence (Figs. 5, 8; Table 2, 3). The partially homogenized inflorescence has primary branches with ramification from third to fifth order (B3, B4 and B5) located at the proximal region, while the primary branches in the middle and distal regions all show the same branch ramification pattern 123 (usually of second or third order) (Figs. 6, 9; Tables 2, 3). In homogenized inflorescences it is possible to recognize two different types of primary branches in the same inflorescence, short paracladia or short primary branches (shB1) and long paracladia or long primary branches (lgB1) (Figs. 5, 6, 8, and 9; Tables 2, 3). In contrast, the nonhomogenized inflorescence does not show specialization of branches (Fig. 7). The inflorescence of the PCK Clade presents different degrees of homogenization depending on the species. For example, the inflorescences of Megathyrsus, Melinis, Yvesia and a few species of Urochloa are non-homogenized; the proximal primary branch may have up to fifth or sixth order ramifications (B5 and B6) (e.g. Megathyrsus and Melinis), which gradually decrease in the primary branches located at the middle and distal regions of the inflorescence (Fig. 7; Tables 2, 4). In contrast, the inflorescences of Inflorescence diversity and evolution in the PCK Clade (Poaceae) 149 Table 2 Presence of the enrichment zone along the synflorescence and different degree of inflorescence homogenization and truncation in the PCK Clade Species Presence/ absence of BTT Trunc. of TS Degree of H Trunc. of shB1 Trunc. of lgB1 Trunc. of ts Brachiaria ambigens Absence No Fully No No No Brachiaria chusqueoides Absence No Non homogenized No No No Brachiaria clavipila Absence No Fully No No No Brachiaria coronifera Presence No Fully No No No Brachiaria dimorpha Absence No Fully No Yes No Brachiaria epacridifolia Absence No Fully No Yes No Brachiaria eruciformis Absence No Partially No No No Brachiaria foliosa Absence No Partially No No No Brachiaria grossa Presence No Partially No No No Brachiaria humbertiana Absence No Fully No No No Brachiaria leucophyrs Absence No Partially No No No Brachiaria longiflora Absence ? Non homogenized ? No No Brachiaria malacodes Absence No Partially No No No Brachiaria marlothii Brachiaria ovalis Absence Presence Yes No Fully Fully Yes No No No No No Brachiaria pseudodichotoma Presence Yes Fully Yes No No Brachiaria pubifolia Absence Yes Fully Yes No No Brachiaria pungipes Absence No Fully Yes No No Brachiaria rugulosa Absence Yes Fully Yes No No Brachiaria scalaris Presence No Fully No No No Brachiaria schoenfelderi Absence No Partially No No No Brachiaria serrata Presence No Fully No No No Brachiaria serrifolia Absence No Fully No No No Brachiaria stigmatisata Presence Yes Fully Yes No No Brachiaria tsiafajavonensis Presence No Partially No No No Brachiaria umbelata Presence No Non homogenized No No No Brachiaria umbralitis Presence No Partially No No No Brachiaria urocoides Absence No Fully No No No Chaetium bromoides Chaetium cubanum Presence Absence No No Partially-fully Fully No No No No No No Eriochloa aristata ? Yes Fully Yes No No Eriochloa distachya ? Yes Fully Yes No No Eriochloa grandiflora ? Yes Fully Yes No No Eriochloa mollis ? Yes Fully Yes No No Eriochloa montevidensis Presence Yes Partially Yes No No Eriochloa polystachia ? Yes Partially Yes No No Eriochloa procera ? Yes Partially Yes No No Eriochloa punctata Presence Yes Fully Yes No No Eriochloa setosa ? Yes Fully Yes No No Eriochloa villosa ? Yes Fully Yes No No Megathyrsus maximus Presence No Non homogenized No No No Melinis leucantha ? No Non homogenized No No No Melinis minutiflora Presence No Non homogenized No No No Melinis monachne Absence No Non homogenized No No No Melinis repens Thuarea involuta Presence Absence No Yes Non homogenized Fully No Yes No No No No 123 150 R. Reinheimer, A. C. Vegetti Table 2 continued Species Presence/ absence of BTT Trunc. of TS Degree of H Trunc. of shB1 Urochloa acuminata Presence No Partially No No No Urochloa adspersa Presence Yes Partially Yes No No Urochloa advena Absence No Fully No No No Urochloa arizonica Urochloa arrecta Presence ? No No Partially Partially No No No No No No Urochloa atrisola Presence Yes Fully Yes No No Urochloa bovonei Absence Yes Fully Yes No No Urochloa brachyura Presence Yes Fully Yes No No Urochloa brizantha Absence Yes Fully Yes No No Urochloa ciliatissima Presence No Fully No No No Urochloa comata Absence No Non homogenized No No No Urochloa decidua Absence No Partially No No No Urochloa decumbens Absence Yes Fully Yes No No Urochloa deflexa Presence No Partially No No No Urochloa dictyoneura Absence Yes Fully Yes No No Urochloa distachya Absence Yes Fully Yes No Yes Urochloa dura Absence Yes Fully Yes No No Urochloa echinolaenoides Absence Yes Fully Yes No No Urochloa eminii Absence No Fully No No No Urochloa fusca Urochloa fusiformis Presence Presence No No Partially Fully No No No No No No Urochloa gilesii Presence Yes Fully Yes No No Urochloa glumaris Absence Yes Fully Yes No No Urochloa holosericea Absence No Fully No Yes No Urochloa humidicola Absence Yes Fully Yes No No Urochloa jubata Absence Yes Fully Yes No No Urochloa kurzii Presence No Fully No No No Urochloa lachnantha Absence No Fully No No No Urochloa lata Presence Yes Fully Yes No No Urochloa leucacrantha Presence No Partially-fully No No No Urochloa lorentziana Presence No Partially No No No Urochloa meziana Presence Yes Fully Yes No No Urochloa mollis Absence No Partially No No No Urochloa mosambicensis Presence Yes Fully Yes No No Urochloa mutica Urochloa nigropedata Presence Absence No Yes Partially Partially No Yes No No No No Urochloa notochthena Presence Yes Fully Yes No No Urochloa oblita Presence No Fully No No No Urochloa oligotricha Absence No Fully No No No Urochloa ophryodes ? Yes Fully Yes No No Urochloa panicoides Presence Yes Fully Yes No No Urochloa paucispicata Absence No Fully No No No Urochloa piligera Presence Yes Fully Yes No No Urochloa plantaginea Presence Yes Partially Yes No No Urochloa platynota Absence Yes Fully Yes No No Urochloa platyphylla Presence Yes Fully Yes No No Urochloa platytaenia Presence Yes Fully Yes No No 123 Trunc. of lgB1 Trunc. of ts Inflorescence diversity and evolution in the PCK Clade (Poaceae) 151 Table 2 continued Species Presence/ absence of BTT Trunc. of TS Degree of H Trunc. of shB1 Trunc. of lgB1 Trunc. of ts Urochloa pratervisa Presence No Fully No No No Urochloa pubigera Absence No Partially No No No Urochloa ramosa Absence No Partially No No No Urochloa rudis Urochloa ruziziensis Absence Absence Yes Yes Fully Fully Yes Yes No No No Yes Urochloa sclerochleaena Presence No Fully No No No Urochloa setigera ? Yes Fully Yes No No Urochloa subulifolia Absence Yes Fully Yes No No Urochloa texana Absence No Fully No No No Urochloa trichopus Presence Yes Fully Yes No No Urochloa venosa Absence No Partially No No No Urochloa villosa Absence No Partially No No No Urochloa whiteana Absence Yes Fully Yes No No Urochloa xantholeuca Absence No Partial No No No Yuesia madagascariensis Absence No Non homogenized No No No 1 1 BTT branch of the trophotagma; H homogenization; shB short primary branch; lgB long primary branch; Trunc. truncation; TS terminal spikelet of the main axis; ts, terminal spikelet at the tip of the primary branch;? missing data Brachiaria, Chaetium, Eriochloa and Urochloa may be, in general, partially or fully homogenized depending on the species (Figs. 5, 6, 8, and 9; Tables 2, 3), while Thuarea has only completely homogenized inflorescences (Fig. 8a; Tables 2, 3). Usually, the degree of homogenization does not vary within a species, but in Chaetium bromoides (J. Presl) Benth. ex Hemsl. and Urochloa leucacrantha (K. Schum.) Stapf this character is polymorphic, varying between partially and fully homogenized depending on the sample studied (Tables 2, 3). Presence or absence of the main axis terminal spikelet In Chaetium, Megathyrsus, Melinis and Yvesia the main axis ends in a terminal spikelet (Fig. 7; Tables 2–4). In contrast, the main axis in Eriochloa and Thuarea may end in a sterile prolongation, in a dome or the most distal primary branch can adopt the terminal position of the main axis as a continuation of it (Figs. 8a, 9c; Tables 2–4). Brachiaria and Urochloa vary in the presence or absence of the terminal spikelet depending on the species (Figs. 5, 6, 8, and 9, 10a, b, e, i; Tables 2–4). Presence or absence of different types of inflorescence branches only by long primary branches (Figs. 8, 9; Table 3). In contrast, in species that are homogenized and have a terminal spikelet, the inflorescence is formed by both long and short primary branches (Figs. 5, 6; Table 3), except for Brachiaria pungipes Clayton, which has the terminal spikelet and long primary branches, but lacks short primary branches (Fig. 5a). Moreover, some inflorescences that are completely homogenized are made up of short primary branches and the terminal spikelet exclusively, and do not develop long primary branches (e.g. B. dimorpha A. Camus, B. epacridifolia (Stapf) A. Camus and U. holosericea (R. Br.) R.D. Webster, Fig. 5b). Presence of a terminal spikelet on the primary branch Like the inflorescence main axis, the primary branches may or may not end in a coflorescence or terminal spikelet (ts). In U. ruziziensis (R. Germ. and Evrard) Crins, we observed that the most distal spikelets on the primary branches, including the terminal spikelet, are abnormally developed and are also sterile at maturity (Fig. 8c). This phenomenon was also observed in some samples of U. brizantha (Hochst. ex A. Rich.) R.D. Webster and U. decumbens (Stapf) R.D. Webster (Fig. 10c, d). Presence of a terminal spikelet on the third order branches Among the homogenized inflorescences, all species that lack the terminal spikelet also lack short primary branches, and in consequence those inflorescences are represented Some species of Eriochloa, Brachiaria and Urochloa (e.g. B. grossa Stapf, B. ovalis Stapf, U. deflexa (Schumach.) 123 152 R. Reinheimer, A. C. Vegetti Fig. 5 Fully homogenized paniculodium (cHP-Type). a cHP1-Subtype (Brachiaria pungipes); b cHP2-Subtype (Brachiaria dimorpha); c cHP3Subtype (Brachiaria scalaris); d cHP4-Subtype (Urochloa advena); e cHP5-Subtype, (Urochloa paucispicata); f cHP6-Subtype (Urochloa sclerochlaena). B2 branch of second order; B3 branch of third order; TS terminal spikelet of the main axis; ts terminal spikelet at the end of the primary branch; lgB1 long primary branch; shB1 short primary branch. The black circle indicates an aborted spikelet H. Scholz, U. lata, U. leucacrantha, U. meziana (Hitchc.) Morrone & Zuloaga, U. oligotricha (Fig. & De Not.) Henrard, U. panicoides P. Beauv, U. texana (Buckley) R.D. Webster and U. trichopus (Hochst.) Stapf) show, at the tip of the third order branches, spikelets that develop abnormally and are sterile at maturity (Fig. 11a). Inflorescence symmetry Members of the PCK Clade show different inflorescence symmetries depending on the orientation of the primary branch along the main axis. The inflorescence may be unilateral (when the inflorescence has only one plane of symmetry, Fig. 1a, c, h, i, o, p), bilateral (with two planes of symmetry, Fig. 1b, f, j, k, n) or radiate (with more than two planes of symmetry, Fig. 1d, e, g, l, m). Number and maximum degree of branch ramification The total number of primary branches and the maximum degree of branch ramification vary extensively among members of the clade and also among different individuals of each studied species. Tables 3 and 4 document the variation in these characters for each species. 123 Orientation of the second order branches on the primary branch This character is easy to interpret in species that have inflorescences with short second order branches and in which the primary branches are more or less flat (Fig. 10h–j). However, it is hard to assess in species that have mature inflorescence with long second order branches and with primary branches that are rounded in cross section. SEM studies show that, early in development and before the elongation of internodes, the second order branches are abaxial on the primary branches (Fig. 11b). Differences in main axis internode length and disposition of the primary branches In Chaetium, Melinis and many species of Brachiaria, Eriochloa and Urochloa, primary branches are always alternate along the main axis. However, because of differences in internode elongation of the main axis during development, the disposition of the primary branches varies widely across the clade and moreover, among the samples studied for each species. At maturity, therefore, the primary branches may appear subopposite (Figs. 6a, 7c) or pseudoverticillate (Fig. 7c). In Tables 3 and 4 we list the Inflorescence diversity and evolution in the PCK Clade (Poaceae) 153 Fig. 6 Partially homogenized paniculodium (pHP-Type). a pHP1Subtype (Urochloa fusca); b pHP2-Subtype (Urochloa xantholeuca); c pHP3-Subtype (Urochloa villosa); d pHP4-Subtype (Brachiaria eruciformis); e pHP4-Subtype (Brachiaria malacodes); f pHP4Subtype (Brachiaria schoenfelderi); g pHP5-Subtype (Urochloa acuminata). B2 branch of second order; B3 branch of third order; B4 branch of fourth order; TS terminal spikelet of the main axis; ts terminal spikelet at the end of the primary branch; lgB1 long primary branch; shB1 short primary branch. The black circle indicates an aborted spikelet disposition of the primary branches along the inflorescence main axis for each species. the longest in comparison with the rest of the internodes of the same primary branch and in consequence, the second order branches are placed far away from the inflorescence main axis (Figs. 6g, 7c). The primary branch and second order branch internodes show length variation in Brachiaria eruciformis (Sm.) Griseb., B. malacodes (Mez & K. Schum.) H. Scholz and B. schoenfelderi C.E. Hubb. & Schweick. (Fig. 6d–f). In B. eruciformis the primary branch internodes are short except for the second proximal internode which is the longest one (Fig. 6d). In B. malacodes, at least the first and the second proximal internodes of the primary branches are long, in comparison with the rest, and also the proximal internodes of the second order branches is the longest one (Fig. 6e). In B. schoenfelderi, the second proximal internode is longer than the remaining internodes that form the primary Differences in the internode length of branches The length of branch internodes varies among members of the clade. In the inflorescence of Melinis (Fig. 7b), pseudoverticils are formed by proximal branch internodes that do not elongate. That is, the most proximal branch internodes develop close to the inflorescence main axis and form false pseudoverticils. These false pseudoverticils are formed by the proximity of second to fifth order branches instead of primary branches. In contrast, in the inflorescences of Megathyrsus maximus and Urochloa acuminata (Renvoize) Morrone & Zuloaga the proximal internode of each primary branch is 123 154 R. Reinheimer, A. C. Vegetti Fig. 7 Non-homogenized paniculodium (nHP-Type). a nHP1-Subtype (Yvesia madagascariensis); b nHP2Subtype (Melinis repens); c nHP3-Subtype (Megathyrsus maximus) (Reproduced by the authorization of American Journal of Botany, Reinheimer et al. 2005). B1 primary branch; B2 branch of second order; B3 branch of third order; B4 branch of fourth order; B5 branch of fifth order; B6 branch of sixth order; dB1 distal primary branch; TS terminal spikelet of the main axis; ts terminal spikelet at the end of the primary branch branches, while the proximal internode of the second order branches is always longer than the rest of the internodes that form that branch (Fig. 6f). Spikelet distribution and organization on the branch In partially or completely homogenized inflorescences, it is easy to assess the distribution and organization of spikelets on the primary branches. In such species the primary branch bears second order branches that may be in one or two rows and may end in a terminal spikelet or may end in a terminal spikelet and have a third order branch at the base. The third order branch may either (1) fail to form a well-developed terminal spikelet; (2) end in a terminal spikelet; or (3) end in a terminal spikelet and develop a new branch (B4) at its base. As a result, depending on the 123 ramification degree of the primary branch and considering the three patterns described above, the spikelets could be solitary in one row (e.g. Thuarea involuta, Fig. 8a), or they could be organized in two rows and be solitary (e.g. some species of Brachiaria, Eriochloa and many species of Urochloa, Fig. 10c, f, g), or solitary with the second spikelet aborted at the base (e.g. Eriochloa punctata (L.) Desv. ex Ham., B. dimorpha, U. adpersa (Trin.) R.D. Webster, U. bulbodes (Steudel) Stapf, U. deflexa (Schumach.) H. Scholz, U. lata, U. panicoides and U. trichopus (Hochst.) Stapf, Fig. 11a) or be paired (e.g. some species of Chaetium, Brachiaria, Eriochloa and Urochloa). In contrast, for species with a non-homogenized inflorescence with more than three orders of branching, the identification of numbers of rows and spikelet organization becomes hard to assess. Inflorescence diversity and evolution in the PCK Clade (Poaceae) 155 Table 3 Inflorescence variation among members of the PCK Clade with fully or partially homogenized inflorescence Species Total N8 N8 of Disposition of B1 lgB1 of B1 Max. branch N8 of Ramification Disposition IF type and degree of B1 shB1 degree of shB1 of shB1 subtype Brachiaria ambigens 11–16 9–10 Alt. and subop. 28 2–3 18, 28 Brachiaria clavipila 8–12 3–4 Alternate 28 5–8 18, 28 Alternate cHP4 Brachiaria coronifera 5–11 4–10 Alt. and subop. 28 1 28 Alternate cHP3 Brachiaria dimorpha 3–7 0–7 Alternate 28 1–4 28 Alternate cHP2 Brachiaria epacridifolia 3–5 0–2 Alternate 28 3 18, 28 Alternate cHP2 Brachiaria eruciformis 1–10 3–10 Alternate 38 9–19 18 Alternate pHP4 Brachiaria foliosa Brachiaria grossa 6–11 6–12 8–9 4–10 Alternate Alternate 38 48 2–3 2–3 18, 28 28 Alternate Alternate pHP3 pHP1 Brachiaria humbertiana 5–8 3–4 Alternate 38 2–4 18, 28 Alternate cHP5 Brachiaria leucophyrs 15 4 Alternate 48 11 18, 28 Alternate pHP1 Brachiaria malacodes 18–22 8–11 Alternate 38 9–11 18 Alternate pHP4 Brachiaria marlothii 5–9 5–9 Alternate 38 _ _ _ cHPT2 Brachiaria ovalis 5–8 3–5 Alternate 38 3–5 18, 28 Alternate cHP6 Brachiaria pseudodichotoma 1–3 1–3 Alternate 28 _ _ _ cHPT4 Brachiaria pubifolia 2–8 2–8 Alternate 28 _ _ _ cHPT4 Brachiaria pungipes 5–8 5–8 Alternate 28 0 _ _ cHP1 Brachiaria rugulosa 3 3 Alternate 28 _ _ _ cH4PT Alternate cHP3 Brachiaria scalaris 4–21 2–19 Alternate 28 1–4 18, 28 Alternate cHP3 Brachiaria schoenfelderi 18–24 8–13 Alternate 38 5–16 18 Alternate pHP4 Brachiaria serrata 5–20 3–16 Alternate 28 2–6 18, 28 Alternate cHP3 Brachiaria serrifolia 6–12 4–9 Alternate 38 1–4 18, 38 Alternate cHP5 Brachiaria stigmatisata Brachiaria tsiafajavonensis 2–5 5–10 2–5 3–6 Alternate Alt. and subop. 28 38 _ 2–5 _ 18, 28 _ Alternate cHPT4 pHP3 Brachiaria umbralitis 10–12 6–8 Alternate 38 3–4 18, 28 Brachiaria urocoides 15–21 3–5 Alternate 28 11–16 18 Chaetium bromoides 9–13 1–6 Alternate 38–48 6–12 18, 28 Alternate cHP6/pHP1 Chaetium cubanum 10 3 Alternate 38 7 18, 28 Alternate cHP6 Eriochloa aristata 5–10 5–10 Alternate 28 _ _ _ cHPT4 Eriochloa distachya 1–2 1–2 Alternate 28 _ _ _ cHPT4 Eriochloa grandiflora 4–6 4–6 Alternate 28 _ _ _ cHPT4 Eriochloa mollis 6 6 Alternate 28 _ _ _ cHPT4 Eriochloa montevidensis 3–13 3–13 Alt. and subop. 38 _ _ _ pHPT3 Eriochloa polystachia 6–20 6–20 Alt. and subop. 38 _ _ _ pHPT3 Eriochloa procera 5–14 5–14 Alternate 38, 48 _ _ _ pHPT1 Eriochloa punctata 5–17 5–17 Alt. and subop. 28 _ _ _ cHPT4 Eriochloa setosa 2 2 Alternate 28 _ _ _ cHPT4 Eriochloa villosa 2 2 Alternate 28 _ _ _ cHPT4 Thuarea involuta Urochloa acuminata 1 28 1 _ 28 24–27 Alt., subop. and pseudov. 38 _ 1–4 _ 18, 28 _ Alternate cHPT1 pHP5 Urochloa adspersa 2–10 2–10 Alt., subop. and pseudov. 48 _ _ _ pHPT1 Urochloa advena 15–18 3 Alternate 28 12–15 18 Alternate cHP4 Urochloa arizonica 9–12 5–8 Alternate 48 4–5 18, 28 Alternate pHP1 Urochloa arrecta ? ? Alt. and subop. 48 ? ? ? pHP1 Urochloa atrisola 2 2 Alternate 28 _ _ _ cHPT4 Urochloa bovonei 1–5 1–5 Alternate 28 _ _ _ cHPT4 Urochloa brachyura 3–9 3–9 Alternate 38 _ _ _ cHPT2 Urochloa brizantha 4 4 Alternate 28 _ _ _ cHPT4/cHPT3 Alternate pHP2 Alternate cHP4 123 156 R. Reinheimer, A. C. Vegetti Table 3 continued Species Total N8 N8 of Disposition lgB1 of B1 of B1 Max. branch N8 of Ramification Disposition IF type and degree of B1 shB1 degree of shB1 of shB1 subtype 28 Urochloa ciliatissima 5–7 3–4 Alternate 3–4 18, 28 Alternate cHP3 Urochloa decidua 30 27 Alt., subop. and pseudov. 48 3 18, 28 Alternate pHP1 Urochloa decumbens 3–7 3–7 Alternate _ _ _ cHPT4/cHPT Urochloa deflexa 6–17 5–15 Alt., subop. and pseudov. 38, 48 1–3 18, 28 Alternate pHP1 Urochloa dictyoneura 3–7 3–7 Alternate 28 _ _ _ cHPT4 Urochloa distachya 4–7 4–7 Alternate 28 _ _ _ cHPT4 Urochloa dura 1–2 1–2 Alternate 28 _ _ _ cHPT4 Urochloa echinolaenoides 1–2 1–2 Alternate 38 _ _ _ cHPT2 Urochloa eminii Urochloa fusca 9–10 4–29 7 3–27 Alt. and subop. 38 Alt., subop. and pseudov. 48 2–3 1–7 18, 28 18, 28 Alternate Alternate cHP5 pHP1 Urochloa fusiformis 5–10 3–8 Alternate 28 1–3 18 Alternate cHP3 Urochloa gilesii 2–3 2–3 Alternate 28 _ _ _ cHPT4 Urochloa glumaris 2–9 2–9 Alt. and subop. 38 _ _ _ cHPT2 Urochloa holosericea 5–7 3–4 Alternate 28 2–3 18, 28 Alternate cHP2 Urochloa humidicola 1–4 1–4 Alternate 28 _ _ _ cHPT4 Urochloa jubata 3–8 3–8 Alternate 28 _ _ _ cHPT4 Urochloa kurzii 5–6 3–4 Alternate 38 2–3 18 Alternate cHP5 Urochloa lachnantha 16 3 Alternate 38 13 28 Urochloa lata 4–7 4–7 Alt., subop. and pseudov. 38 _ _ _ cHPT2 Urochloa leucacrantha 1–11 1–6 Alternate 28, 38 1–5 18, 28 Alternate cHP5/pHP2 Urochloa lorentziana 4–31 4–30 Alt., subop. and pseudov. 48, 58 1–5 18, 28 Alternate pHP1 Urochloa meziana 4–8 4–8 Alt. and subop. 28 _ _ _ cHPT4 Urochloa mollis 5–14 3–9 Alternate 38 1–6 18, 28 Alternate pHP2 Urochloa mosambicensis Urochloa mutica 2–15 5–31 2–15 8–27 Alternate 28 Alt., subop. and pseudov. 38, 48 _ 3–7 _ 18, 28 _ Alternate cHPT4 pHP1 Urochloa nigropedata 3–8 Alternate 38 _ _ _ pHPT2 Urochloa notochthena 2–3 2–3 Alternate 28 _ _ _ cHPT4 Urochloa oblita 6–12 3–6 Alternate 38 3 28 Alternate cHP5 Urochloa oligotricha 52–62 14–18 Alternate 38 36–44 18, 38 Alternate cHP6 Urochloa ophryodes 2–3 2–3 Alternate 28 _ _ _ cHPT4 Urochloa panicoides 2–9 2–9 Alt. and subop. 28 _ _ _ cHPT4 Urochloa paucispicata 9–12 4–8 Alternate 38 1–5 18, 28 Alternate cHP5 Urochloa piligera 2–4 2–4 Alternate 28 _ _ _ cHPT4 Urochloa plantaginea 2–14 2–14 Alternate 28, 38 _ _ _ pHPT2 Urochloa platynota 2–3 2–3 Alternate 28 _ _ _ cHPT4 Urochloa platyphylla 2–6 2–6 Alternate 28 _ _ _ cHPT4 Urochloa platytaenia 2–9 2–9 Alternate 28 _ _ _ cHPT4 Urochloa pratervisa 8–13 8–9 Alternate 38 4–5 18, 28 Alternate cHP5 Urochloa pubigera Urochloa ramosa 22 10–12 15 7–10 Alternate Alt. and subop. 38 48 7 2–3 18, 28 18, 28 Alternate Alternate pHP2 pHP1 Urochloa rudis 4 4 Alternate 28 _ _ _ cHPT4 Urochloa ruziziensis 1–5 1–5 Alternate 28 _ _ _ cHPT3 Urochloa sclerochleaena 7 1–2 Alternate 38 5–6 18, 28 Alternate cHP6 Urochloa setigera 3–6 3–6 Alternate 38 _ _ _ cHPT2 Urochloa subulifolia 2–3 2–3 Alternate 28 _ _ _ cHPT4 Urochloa texana 9–14 8–11 Alternate 38 2–5 18, 28 Alternate cHP5 Urochloa trichopus 4–13 4–13 Alternate 28 _ _ _ cHPT4 123 28 cHP6 3 Inflorescence diversity and evolution in the PCK Clade (Poaceae) 157 Table 3 continued Species Total N8 N8 of Disposition lgB1 of B1 of B1 Max. branch N8 of Ramification Disposition IF type and degree of B1 shB1 degree of shB1 of shB1 subtype Urochloa venosa 10–14 8–10 Alt. and subop. 48 3–4 18, 28 Alternate pHP1 Urochloa villosa 5–11 3–9 Alt. and subop. 28, 38 1–3 18 Alternate pHP3 Urochloa whiteana 2 2 Alternate 28 _ _ _ cHPT4 Urochloa xantholeuca 3–14 2–13 Alternate 38 1–3 28 Alternate pHP2 18 ramification up to first order; 28 ramification up to second order; 38 ramification up to third order; 48 ramification up to fourth order; 58 ramification up to fifth order; alt. alternate; B1 primary branch; IF inflorescence; lgB1 long primary branch; Max. maximum; N8 number; pseudov. pseudoverticillate; shB1 short primary branch; subop. subopposite; ? missing data Total number, ramification degree and phyllotaxis of the most distal primary branch of the inflorescence In species that have a terminal spikelet on the main axis, the primary branches below the terminal spikelet vary extensively in number and ramification among the species and even among the samples of each species. In species with homogenized inflorescences, the primary branches located below the terminal spikelet are short primary branches, which, in general, may not have ramification or may have ramifications up to second order (Figs. 5, 6) (exceptionally, third order, e.g. Brachiaria serrifolia (Hochst.) Stapf and Urochloa oligotricha). In contrast, for inflorescences that are non-homogenized we used the term distal paracladia or distal branches (dB) to describe the branches that are located under the terminal spikelet. In these cases, the distal primary branch may not have ramification or may have ramifications up to fouth order (Fig. 7). In all species studied, the most distal branches (short primary branch or distal primary branch) have an alternate disposition on the inflorescence main axis. In Tables 3 and 4 we describe in detail the range of variation shown by the distal primary branches across the PCK Clade. Types and subtypes of the PCK Clade inflorescences Based on the characters described above, we identify different inflorescence types in the clade, all of which are variations of a basic paniculodium. The inflorescences of the PCK Clade can be classified in two main groups: (a) inflorescences with a terminal spikelet (Paniculodium Type, P) and, (b) inflorescence without a terminal spikelet (Truncated Paniculodium Type, TP). Within the P Type group, the inflorescence may be: (a0 ) a completely Homogenized paniculodium (cHP), (a00 ) partially Homogenized Paniculodium (pHP), and ða000 Þ non-Homogenized Paniculodium (nHP). Within the TP Type we observed that the inflorescences are (b0 ) completely (cHPT) or (b00 ) partially Homogenized (pHPT). In consequence, we found five different, basic inflorescence types, among which we recognized at least 21 different inflorescence subtypes across the clade based on the rest of the characters selected. Inflorescences types and subtypes found are described in the following key: 1 Inflorescence without a terminal spikelet 2 10 Inflorescence with a terminal spikelet 13 2(1) Inflorescence completely homogenized (cHP) 3 20 Inflorescence partially homogenized (pHP) 7 200 Inflorescence not homogenized 11 (nHP) 3(2) Inflorescence represented by long primary branches and short primary branches 4 30 Inflorescence represented cHP1-Subtype exclusively by long primary (eg. B. pungipes, Fig. 5a) branches 300 Inflorescence represented cHP2-Subtype exclusively by short primary (eg. B. dimorpha, Fig. 5b) branches 4(3) Ramifications up to second order, solitary spikelets 40 5 Ramifications up to third order, 6 paired spikelets 5(4) Equal or higher number of long primary branches than short primary branches 50 Higher number of short primary branches than long primary branches cHP3-Subtype (eg. B. scalaris Pilg., Fig. 5c) cHP4-Subtype (eg. U. advena (Vickery) R.D. Webster, Fig. 5d) 6(40 ) Equal or higher number of long cHP5-Subtype primary branches than short (eg. U. paucispicata primary branches (Morong) Morrone & Zuloaga, Fig. 5e) 60 Higher number of short primary branches than long primary branches cHP6-Subtype (eg. U. sclerochlaena Chiov. ex Chiarugi, Fig. 5f) 123 158 7(20 ) 70 R. Reinheimer, A. C. Vegetti Primary branches and second 8 order branches with equal internode lengths 18(17) Higher number of solitary spikelets than paired spikelets on long primary branches Primary branches and second 10 order branches with different internode lengths 180 8(7) Ramifications up to third order 80 Ramifications up to fourth or pHP1-Subtype exceptionally fifth order (eg. U. fusca (Sw.) B.F. Hansen and Wunderlin, Fig. 6a) 9(8) 90 Higher number of solitary spikelets than paired spikelets on long primary branches Higher number of paired spikelets than solitary spikelets on long primary branches 9 pHP2-Subtype (eg. U. xantholeuca (Hack. ex Schinz) H. Scholz, Fig. 6b) pHP3-Subtype (eg. U. villosa(Lam.) T.Q. Nguyen, Fig. 6c) 10(70 ) Equal or higher number of pHP4-Subtype short primary branches than (eg. B. eruciformis, Fig. 6d) long primary branches 100 Higher number of long pHP5-Subtype (eg. U. acuminata, Fig. 6g) primary branches than short primary branches 11(200 ) Ramifications up to second order (eg. Yvesia, Fig. 7a) 110 2 Ramifications up to fifth or sixth order nHP1-Subtype 12(110 ) Presence of short proximal internodes on primary branches nHP2-Subtype 120 Presence of long internodes on primary branches nHP3-Subtype 13(10 ) Completely homogenized inflorescence (cHPT) 14 130 Partially homogenized inflorescence (pHPT) 17 (eg. Melinis, Fig. 7b) (eg. Megathyrsus, Fig. 7c) 14(13) Presence of a spathaceous bract. cHPT1-Subtype (eg. Thuarea, Fig. 8a) 140 15 Absence of a spathaceous bract 15(140 ) Ramifications up to second order (solitary spikelets) 16 150 cHPT2-Subtype Ramifications up to third order (pared spikelets) 16(15) With truncation of the Cof (eg. B. marlothii (Hack.) Stent, Fig. 8b) cHPT 3-Subtype (eg. U. ruziziensis, Fig. 8C) 160 Without truncation of the Cof cHPT4-Subtype (eg. U. platyphylla (R. Br.) R.D. Webster, Fig. 8d) 17(130 ) Ramifications up to third order 170 Ramifications up to fourth order 123 18 pHPT1-Subtype (eg. U. adspersa, Fig. 9a) pHPT2-Subtype (eg. U. plantaginea (Link) R.D. Webster, Fig. 9b) Higher number of paired pHPT3-Subtype spikelets than solitary spikelets (eg. E. montevidensis on long primary branches Griseb., Fig. 9c) Each subtype may include more than one species; within a subtype, species may differ from each either by the number and disposition of the primary branches and by the number and ramification degree of the short primary branches or distal primary branches (Tables 3, 4). Discussion The synflorescence The limits of what an inflorescence should be are a complex and confused matter and are still somewhat subjective (Weberling 1965, 1989; Rua 1999; Buzgo et al. 2004). In the first work of Troll (1964), that controversy was already considered when the author proposed the term synflorescence in place of the term inflorescence. Troll’s model assumes that the inflorescence in the context of the whole shoot system originated from the apical bud of the main axis or from axillary buds (innovations) located along the main axis (Troll and Weberling 1989). The synflorescence of the PCK Clade has different zones already described for other grasses (Troll 1966, 1969; Troll and Weberling 1989; Rua 1999): (1) the innovation zone, (2) the inhibition zone, (3) the enrichment zone (not present in some species), and (4) the terminal inflorescence. Nowadays it is well known that the architecture of the grass synflorescence is controlled by the expression of several genes, for example ramosa1 (ra1), teosinte branched1 (tb1), barren stalk1 (ba1), indeterminate spikelet1 (ids1), branched silkless1 (bd1), liguleless2 (lg2), fascinated ear2 (fea2), thick tassel dwarf1 (td1) and knotted1 (kn1) among others. All these genes encode transcription factors that affect synflorescence architecture, modifiying the temporal development of the different zones or by regulating meristem sizes (Poeting 1990; Doebley et al. 1997; Chuck et al. 1998, 2002; Walsh and Freeling 1999; Vollbrecht et al. 2000; Taguchi-Shiobara et al. 2001; Gallavotti et al. 2004; Bommert et al. 2005; Vollbrecht et al. 2005). The grass synflorescence may or may not have branches of the trophotagma along the enrichment zone (Vegetti and Müller-Doblies 2004). In the PCK Clade, this character varies among the different species, is not exclusive for one Inflorescence diversity and evolution in the PCK Clade (Poaceae) 159 Fig. 8 Fully homogenized truncated paniculodium (cHPTType). a cHPT1-Subtype (Thuarea involuta); b cHPT2Subtype (Brachiaria marlothii); c cHPT3-Subtype (Urochloa ruziziensis); d cHPT4-Subtype (Urochloa platyphylla). B2 branch of second order; B3 branch of third order; ts terminal spikelet at the end of the primary branch; lgB1 long primary branch; shB1 short primary branch. The asterisk indicates absence of a terminal spikelet on the main florescence. The black circle indicates an aborted spikelet genus and does not correlate with plant life history; within the clade, there are perennial and annual plants that may or may not have branches of the trophotagma. Frank (1998) analyzed the correlation between the presence of branches of the trophotagma and the climate in which the plant grows, and concluded that the absence of branches of the trophotagma correlated with tropical climate or arid and dry habitats (e.g. steppe). Also, those species that lack branches of the trophotagma do not grow in regions with high variation in temperature and humidity. Thus, the development of branches of the trophotagma may be directly correlated with humidity gradients. The structure of the adult inflorescence The inflorescence in the PCK Clade is polytelic (lacking the terminal flower) as was described also for the Poaceae (Troll 1966, 1969; Cámara Hernández and Rua 1991; Vegetti 1991a, b) and for several monocotyledonous inflorescences. In the PCK Clade, the main axis of the polytelic inflorescence may or may not end in a terminal spikelet. When the main axis develops a terminal spikelet, the inflorescence is a non-truncated paniculodium (P), while when the main axis lacks the terminal spikelet the inflorescence became a truncated paniculodium (TP). The PCK Clade is a well-supported monophyletic group (Gómez-Martinez and Culham 2000; Zuloaga et al. 2000; Duvall et al. 2001; Giussani et al. 2001) but is surprisingly diverse in inflorescence structure. We have identified at least 21 different mature inflorescence subtypes within the clade; in addition, some genera exhibited more than one inflorescence type. We found fourteen characters that vary across the different genera and species in the clade: (1) presence or absence of a spathaceous bract, (2) inflorescence symmetry, (3) total number of the primary branches, (4) maximum branch degree of the primary branches, (5) phyllotaxis of the primary branches, (6) differences in branch internode length, (7) spikelet distribution and organization on branches, (8) total number of the most distal primary branches, (9) ramification degree of the most distal primary branches of the inflorescence, (10) degree of homogenization of the inflorescence, (11) presence or absence of the terminal spikelet of the main axis, (12) presence or absence of the terminal spikelet at the end of primary branches, (13) presence or absence of the terminal spikelet at the tip of third order branches, and (14) presence or absence of different types of branches. Among these characters, some are unique for one species, others vary among species and others are polymorphic in the same species as we describe below. In contrast, the orientation of the second order 123 160 R. Reinheimer, A. C. Vegetti Table 4 Inflorescence variation among members of the PCK Clade with non-homogenized inflorescence Species Total N8 of B1 Disposition of B1 Max. branch degree of B1 N8 of dB1 Ramification degree of dB1 Disposition of dB1 IF type and subtype Alternate 28 2 18, 28 Alternate nHP1 nHP1 Brachiaria chusqueoides 4–6 Brachiaria longiflora 3–5 Alternate 28 2 18 Alternate Brachiaria umbelata 4–17 Alternate 28 2–3 18 Alternate nHP1 Megathyrsus maximus 18–56 Alt., subop. and pseudov. 58 1–3 18, 48 Alternate nHP3 Melinis leucantha 9–12 Alternate 58 2–3 18, 28 Alternate nHP2 Melinis monachne 7–10 Alternate 58 2 18 Alternate nHP2 Melinis minutiflora Melinis repens 9–21 8–22 Alternate Alternate 68 68 2–3 2–3 18, 28 18, 28 Alternate Alternate nHP2 nHP2 11–19 Alternate 58 1 18 _ nHP2 Alt. and subop. 28 1 18 _ nHP1 Urochloa comata Yvesia madagascariensis 3–6 18 ramification up to first order; 28 ramification up to second order; 48 ramification up to fourth order; 58 ramification up to fifth order; 68 ramification up to sixth order; alt. alternate; B1 primary branch; dB1 distal primary branch; IF inflorescence unit; Max. maximum; N8 number; pseudov. pseudoverticillate; subop. subopposite branches on the primaries does not show variation in the clade. All the species have second order branches abaxially orientated on primary branches, as was also reported by Reinheimer (2007). Thuarea involuta is the only species that develops a spathaceous bract subtending the unique primary branch that forms its inflorescence. In general, the grass inflorescence has branches usually subtended by bracts that fail to develop. Whether the bract in Thuarea is one that fails to be repressed may be elucidated by ontogenetic studies. Inflorescence symmetry has been used as one of the most important characters in the taxonomic delimitation of the American species of Brachiaria and Urochloa (Morrone and Zuloaga 1992, 1993). However, developmental studies show that the symmetry is an intricate character to assess within the PCK Clade because it is directly correlated with the initiation pattern of the primary branches. In the group, the development of primary branches and with that, the specification of inflorescence symmetry, are diverse and complex processes that will be treated in a separate work (Reinheimer 2007). Inflorescences in the PCK Clade vary extensively in the number of primary branches and maximum branch degree. These characters diverge among different genera, among species within the same genus, and among specimens of the same species. In general, the total number of primary branches varies from 1 to 24 in Brachiaria, 1–62 in Urochloa, 1–20 in Eriochloa, 9–13 in Chaetium, 18–56 in Megathyrsus, 8–22 in Melinis, 3–6 in Yvesia and only 1 in Thuarea. In most cases, the maximum branch degree correlates with the homogenization level of the inflorescence. Usually, the primary branches are alternate along the inflorescence main axis. However, depending on the degree of internode elongation of the main axis during 123 development, some primary branches appear subopposite or pseudoverticillate in many species. The variation in internode length has been observed also along the inflorescence branches of some members of the Clade. Thus, some species may present differential internode elongation only along the main axis (e.g. Urochloa fusca), some may have different internode lengths only along the branches (e.g. Brachiaria eruciformis), or some may show variation of internode length on the main axis and branches of the inflorescence (e.g. Megathyrsus maximus). Furthermore, in some species (e.g. Melinis) since the proximal internode of each branch does not elongate, false pseudoverticels are formed by the proximity of second to fifth order branches intead of primary branches. As was already mentioned by Malcomber et al. (2006) and based on several ontogenetic studies (Fraser and Kokko 1993; Doust and Kellogg 2002a, b; Ikeda et al. 2004; Bess et al. 2005; Kellogg et al. 2004; Reinheimer et al. 2005; Sörenson et al., unpublished data), in grasses the elongation of internodes of the main inflorescence axis is independent of that of primary branches and secondary branches. Moreover, in grasses the elongation of the internodes occurs late in development when branches, spikelets and flowers are already formed (Reinheimer 2007). These results suggest that the elongation of the internodes is thus genetically distinguishable from the specification of branch and spikelet identity. Until now, a few genes (e.g. panicle phytomer1) and several QTL have been identified as responsible for differences in internode elongation (Takahashi et al. 1998; Doust et al. 2005). In some members of the PCK Clade we identified inflorescences that bear solitary spikelets along the primary branches and others that have paired spikelets, placed in one or two rows. That organization can be easily assessed in those mature inflorescences that have somewhat Inflorescence diversity and evolution in the PCK Clade (Poaceae) 161 Fig. 9 Partially homogenized truncated paniculodium (pHTPType). a pHTP1-Subtype (Urochloa adspersa); b pHTP2Subtype (Urochloa plantaginea); c pHTP3-Subtype (Eriochloa montevidensis). B2 branch of second order; B3 branch of third order; B4 branch of fourth order; ts terminal spikelet at the end of the primary branch coflorescence; lgB1 long primary branch; shB1 short primary branch. The asterisk indicates absence of a terminal spikelet on the main florescence. The black circle indicates an aborted spikelet flattened primary branches and short secondary branches, while it is hard to evaluate in inflorescences that are profusely branched and with long branches. Developmental studies, certainly, will help us to determine the spikelet organization along the primary branches early in development before the elongation of the internodes. In the P Type inflorescence, we found short primary branches or distal primary branches placed immediately below the terminal spikelet of the main axis (except in B. pungipes). Depending on the species and the specimen studied, these types of branches are high variable in number and may not have ramifications or may have up to fourth order branches. In consequence, the ramification degree of the most distal branches of the inflorescence is polymorphic even among samples of the same species. Among the different structures found in the inflorescence of the PCK Clade, we identified at least nine different evolutionary trends that have already been described for Poaceae (Vegetti and Anton 1995, 2000). These trends are, at least in part, responsible for the diversity in the inflorescences of the clade: (1) presence or absence of the terminal spikelet of the main axis, (2) presence or absence of the terminal spikelet at the end of the primary branches, (3) presence or absence of long branches, (4) presence or absence of short primary branches, (5) branch homogenization, (6) increase or decrease in inflorescence ramification, (7) differential elongation of main axis internodes, (8) differential elongation of branch internodes, and (9) presence or absence of a spathaceous bract. The absence of distal structures along the main axis and primary branches (also called truncation) and the 123 162 R. Reinheimer, A. C. Vegetti Fig. 10 Photograph of the inflorescence of Urochloa. a sterile main axis prolongation in the truncated paniculodium of U. decumbens; b truncated paniculodium of U. lata; c abnormal coflorescence of a long primary branch in U. decumbens; d detail of the abnormal coflorescence in c; e truncated paniculodium in U. platyphylla; f solitary spikelets in two rows on the abaxial side of a long primary branch of U. mosambicensis; g solitary spikelets in two rows on the abaxial side of a long primary branch of U. brizantha; h flat primary branch in U. mosambicencis; i sterile main axis prolongation in the truncated paniculodium and spikelets with abaxial orientation on the long primary branch U. jubata; j spikelets with abaxial orientation on the long primary branch U. mollis. ts terminal spikelet at the end of the primary branch; lgB1 long primary branch; Ma main axis; Spk normal spikelet. The white asterisk indicates absence of a terminal spikelet on the main axis. The black asterisk indicates the abnormal terminal spikelets at the tip of a long primary branch morphological similarity of inflorescence branches (called homogenization) have been proposed as common evolutionary processes in the angiosperms (Troll 1964, 1969; Weberling 1965, 1985; Maresquelle 1970; Sell 1976; Kunze 1989; Vegetti and Anton 1995, 2000). Moreover, these trends have been considered responsible, at least in part, for the great inflorescence diversity seem among the angiosperms (Troll 1964, 1969; Maresquelle 1970; Sell 1976; Weberling 1965, 1985; Kunze 1989; Vegetti and Anton 1995, 2000). (Goebel 1931; Troll 1966, 1969; Cámara Hernández and Rua 1991; Vegetti 1991a, b; Cámara Hernández and Miante–Alzogaray 1994) or even more, the distal flower systems (spikelet) of the main axis or branches and may also entire branches. Kunze (1989) suggested different types of polytelic inflorescences according to the different levels of truncation mentioned. In the PCK Clade, we found non-truncated inflorescences, and inflorescences that lack different parts. Among the latter, we observed truncation of (1) the terminal spikelet of the inflorescence main axis, (2) the entire primary branches (including long primary branches or short primary branches) and (3) distal parts of the primary branches. These patterns are not restricted to the PCK Clade; they have also been recorded for other members of subfamily Panicoideae, as well as members of subfamily Chloridoideae among Truncation The grasses show different levels of truncation (loss of different inflorescence structures). For example, several grass species lack the terminal flower of the spikelet 123 Inflorescence diversity and evolution in the PCK Clade (Poaceae) 163 Fig. 11 Scanning electron micrographs. a Primary branch of Urochloa lata showing the aborted spikelets at the base of branch of third order. b Primary branch of Megathyrsus maximus showing the abaxial disposition of secondary branches. aSpk aborted spikelet; B2 secondary branch; B3 branch of third order; ts terminal spikelet at the end of the primary branch; lgB1 long primary branch; nSpk normal spikelet others (Vegetti 1987; Vegetti and Pensiero 1990; Vegetti 1991a; Rua 1993, 1996; Rua and Boccaloni 1996; Perreta and Vegetti 1998; Rua and Weberling 1998; Vegetti 1999; Giraldo-Cañas 2000; Cámara Hernández 2001; Pensiero and Vegetti 2001; Liu et al. 2005). The inflorescence of Chaetium, Melinis, Megathyrsus and Yvesia, are P type paniculodia, while Eriochloa and Thuarea are always TP type paniculodia. In constrast, Brachiaria and Urochloa showed P and TP type paniculodia depending on the species examined. All species of Brachiaria that have TP inflorescence are African, except for B. rugulosa, which is Australian. Also, the majority of the Urochloa species that have TP are originally from Africa (except for U. adpersa, U. meziana, U. ophryodes (Chase) Morrone & Zuloaga and U. platyphylla which are American species). When the inflorescence P and TP are compared, we observed that in all the inflorescences that lack the terminal spikelet the distal branches (which should be immediately below the terminal spikelet) are also not developed. We found two morphologies that were novel for the PCK Clade (the subtype cHP1 and the subtype cHP2) and also for the tribe Paniceae. Brachiaria pungipes, an African species, has a P type inflorescence made up by the terminal spikelet and long primary branches exclusively. When we compared this subtype with other cHP type inflorescence, we noticed that the inflorescence of B. pungipes lacks short primary branches. In contrast, the inflorescence of B. dimorpha, B. epacridifolia and U. holosericea, lack the long primary branches, since their inflorescences are only represented by the terminal spikelet and short primary branch. The first two species are originally from Africa, and U. holosericea is an Australian species. Future studies should investigate the origin of the terminal spikelet of B. pungipes; it could be a true terminal spikelet or a lateral short primary branch which has adopted a terminal position on the main axis. In the same way, new studies should address the origin of the ramification system of B. dimorpha, B. epacridifolia and U. holosericea, since the entire inflorescence could be also considered to be a unique long primary branch which has acquired the position of the inflorescence main axis. However, we observed neither a pulvinulus nor bracts; there is thus no real evidence for the latter hypothesis. Developmental studies may be a useful tool to investigate and corroborate these hypotheses. Another level of truncation was observed in some species of Urochloa, in which the inflorescence presents long primary branches that lack well developed distal spikelets (including the terminal one). This pattern is constant among all examined samples of U. ruziziensis, whereas it varies among samples of U. brizantha and U. decumbens. Possibly in the last two species the truncation of the distal part of the long primary branch may be conditioned by environmental factors rather than being genetically and ontogenetically fixed as in U. ruziziensis. Ontogenetic studies in the PCK Clade revealed that the abnormal spikelets follow different and complex patterns of development depending on their position on the inflorescence and the examined species; a full description of such spikelets is treated elsewhere (Reinheimer 2007). Homogenization Homogenization, that is similarities among the inflorescence branches, is an evolutionary process which determines, in part, the general appearance of the inflorescence. Such process has been found in different groups of Poaceae, as in subfamily Panicoideae (Rua 1993, 1996; Rua and Weberling 1998; Vegetti 1991a; Pensiero and Vegetti 2001) as well as in other subfamilies, for example in Chloridoideae (Perreta and Vegetti 1998; Cámara Hernández 2001; Liu et al. 2005) and Ehrhartoideae (Vegetti and Pensiero 1999; Vegetti 2000). Different degrees of homogenization are found among species of the PCK Clade. We found three levels of 123 164 homogenization: non-homogenized inflorescence, partially homogenized inflorescence, and completely homogenized inflorescence. The partially homogenized inflorescence has been considered as a transition or intermediate form between the non-homogenized inflorescence and the fully homogenized inflorescence (Rua 1996; Rua and Weberling 1998; Reinheimer and Vegetti 2004). An intermediate form of homogenization has been also observed in other genera of Paniceae (e.g. Panicum L. and Paspalum L.) (Rua 1996; Rua and Weberling 1998; Reinheimer and Vegetti 2004). As a direct consequence of the different degrees of homogenization, the inflorescence may or may not be disjunct. Non-homogenized inflorescences do not show disjunction, while partially or fully homogenized inflorescences are disjunct, such that it is possible to identify long primary branches and short primary branches. Many authors have observed a correlation between homogenization and truncation (Vegetti 1991a; Rua and Weberling 1998; Vegetti and Anton 2000). In this study, however, we found that the correlation is asymmetric. In the PCK Clade, we observed that all truncated inflorescences are also homogenized, but all inflorescences that are homogenized are not necessarily truncated. For example, many species of Brachiaria, Urochloa and Chaetium have homogenized inflorescences without any sign of truncation. In contrast, all species of Eriochloa, Thuarea involuta and some species of Brachiaria and Urochloa show a direct correlation between homogenization and truncation as was observed in other members of Panicoideae (e.g. Setaria P. Beauv., the majority of Paspalum species, and members of Andropogoneae) (Rua 1993, 1996; Rua and Weberling 1998, Vegetti 1999; Pensiero and Vegetti 2001), and species of Chloridoideae (e.g. Leptochloa P. Beauv. and Digitaria Haller) (Perreta and Vegetti 1998; Cámara Hernández 2001; Liu et al. 2005). Inflorescence structure and taxonomy of the PCK Clade Chaetium presented a cHP6-Subtype inflorescence (fully homogenized paniculodium with higher number of short primary branches than long primary branches) or rarely a pHP1-Subtype inflorescence (partially homogenized paniculodium with ramifications up to fourth order). All the species of Melinis studied in this work have inflorescences that are nHP2-Subtype (non-homogenized paniculodium with short proximal internodes of the primary branches). Also, the inflorescence of Megathyrsus is an nHP3-Subtype (non homogenized paniculodium with the first proximal internode longer than the rest of the internodes that form the branch), the inflorescence of Thuarea belongs to the cHPT1Subtype (truncated and fully homogenized paniculodium with a spathaceous bract), and the inflorescence of Yvesia fits into the nHP1-Subtype (non-homogenized paniculoidium 123 R. Reinheimer, A. C. Vegetti with ramifications up to second order). We were unable to find any inflorescence characters that allowed us to distinguish Brachiaria clearly from Urochloa. Moreover, the nHP1-Subtype is also present in three species of Brachiaria (B. chusqueoides (Hack.) Clayton, B. longiflora Clayton and B. umbelata (Trin.) Clayton). The nHP2-Subtype characteristic of Melinis is also present in one Urochloa species, U. comata (Hochst. ex A. Rich.) Stapf. The cHP6-Subtype represented by Chaetium was also found in Brachiaria ovalis Stapf and some species of Urochloa (U. lachnantha (Hochst.) A.M. Torres & C.M. Morton, U. oligotricha and U. sclerochlaena). Inflorescence evolution in the PCK Clade The most recent phylogeny of the PCK Clade, based on the nuclear ITS and 5.8S regions, suggests that Brachiaria and Melinis may be sister to each other, and the Brachiaria/ Melinis clade may be sister to the rest of the PCK species. Urochloa may be paraphyletic and associated with Megathyrsus and Eriochloa (Torres González and Morton 2005). If this phylogeny is correct, then inflorescence morphology tends to become simpler during the evolution of the clade. That is, highly branched, non-truncated inflorescences with differences in internode lengths (e.g. pHP4, nHP2, nHP3) are present in the genera Brachiaria and Melinis, and also in Megathyrsus which is sister to the Urochloa, and Eriochloa group. Truncated inflorescence morphologies (e.g. pHPT3, cHPT4, cHPT3, pHPT2), appear late in the history of the clade. The phylogeny of Torres Gonzalez and Morton is not well-supported, however, and thus a reliable assessment of changes in the inflorescence is still lacking. Furthermore, inflorescence development in the PCK Clade shows considerable variation among its members (Stür 1986; Reinheimer et al. 2005; Reinheimer 2007). As a consequence, further studies––including ontogenetic and gene expression studies––will be necessary to understand how, when and where modifications during development occur to create the extensive adult inflorescence variation described in this work. Acknowledgments The authors thank Elizabeth A. Kellogg and two anonymous reviewers for critical reading of the manuscript and for her helpful comments. We also are grateful to Osvaldo Morrone and CIAT for access to plant materials of Urochloa lata. Financial support was provided by UNL - CAID + D 2006 (to R.R.), UNLCAID + D 2002 (to A.V) and PIP-CONICET 2935/00 (to A.V). References Aliscioni SS, Giussani LM, Zuloaga FO, Kellogg EA (2003) A molecular phylogeny of Panicum (Poaceae: Paniceae): test of monophyly and phylogenetic placement within the Panicoideae. Amer J Bot 90:796–821 Inflorescence diversity and evolution in the PCK Clade (Poaceae) Ambrose BA, Lerner DR, Ciceri P, Padilla CM, Yanofsky MF, Schmidt RJ (2000) Molecular and Genetic analyses of the silky1 gene reveal conservation in floral organ specification between eudicots and monocots. Mol Cell 5:569–579 Arriaga MO (2000) Austral South American species of Eriochloa. In: Jacobs SWL, Everett J (eds) Grasses: systematics and evolution. CSIRO, Melbourne, pp 141–148 Beauvois P (1812) Urochloa. Essai d’une Nouvelle Agrostographie 11: 52 Bess EC, Doust AN, Kellogg EA (2005) A naked grass in the ‘‘Bristle Clade’’: A phylogenetic and developmental study of Panicum section Bulbosa (Paniceae: Poaceae). Int J Pl Sci 166:371–381 Bommert P, Lunde C, Nardmann J, Vollbrecht E, Running M, Jackson D, Hake S, Werr W (2005) thick tassel dwarf1 encodes a putative maize ortholog of the Arabidopsis CLAVATA1 leucinerich repeat receptor-like kinase. Development 132:1235–1245 Buzgo M, Soltis DE, Soltis PS, Ma H (2004) Towards a comprehensive integration of morphological and genetic studies of floral development. Trends Pl Sci 9:164–173 Cámara Hernández J (2001) Morfologı́a de la inflorescencia de Digitaria sanguinalis (L.) Scop. (Poaceae). Bol Soc Argent Bot 36:87–95 Cámara Hernández J, Rua GH (1991) The synflorescence of Poaceae. Beitr Biol Pflanz 66:297–311 Cámara Hernández J, Miante-Alzogaray A (1994) Polytely: a general character in Poaceae. Beitr Biol Pflanz 68:249–261 Chuck G, Meeley R, Hake S (1998) The control of maize spikelet meristem identity by the APETALA-2 like gene indeterminate spikelet1. Genes Dev 12:1145–1154 Chuck G, Muszynski M, Kellogg EA, Hake S, Schmidt RJ (2002) The control of spikelet meristem identity by branched silklees1 gene in maize. Science 298:1238–1241 Clayton WD, Renvoize SA (1982) Flora of Tropical East Africa: Gramineae, part 3. A. A Balkema, Rotterdam, pp 451–898 Clayton WD, Renvoize SA (1986) Genera graminum: grasses of the world. Kew Bull, Add Ser 13:1–389 Davidse G (1987) Fruit dispersal in the Poaceae. In: Soderstrom TR, Hilu KW, Campbell CS, Barkworth ME (eds) Grass systematics and evolution. Smithsonian Inst. Press, Washington, pp 143–155 Davidse G (1993) Poaceae. In: Brako L, Zarucchi JL (eds) Catalogue of the flowering plants and gymnosperms of Peru. Monogr Syst Botany Missouri Botanical Garden 45:1258 Doebley J, Stec A, Hubbard L (1997) The evolution of apical dominance in maize. Nature 386:485–488 Doust AN, Kellogg EA (2002a) Integrating phylogeny, developmental morphology and genetics: a case study of inflorescence evolution in the ‘‘bristle grass’’ clade (Panicoideae: Poaceae). In: Cronk QCB, Bateman RM, Hawkins JA (eds) Developmental genetics and plant evolution. Taylor and Francis, London, pp 298–314 Doust AN, Kellogg EA (2002b) Inflorescence diversification in the panicoid ‘‘bristle grass’’ clade (Paniceae, Poaceae): evidence from molecular phylogenies and developmental morphology. Amer J Bot 89:1203–1222 Doust AN, Drinnan AN (2004) Floral development and molecular phylogeny support the generic status of Tasmannia (Winteraceae). Amer J Bot 91:321–331 Doust AN, Devos KM, Gadberry MD, Gale MD, Kellogg EA (2005) The genetic basis for inflorescence variation between foxtail and green millet (Poaceae). Genetics 169:1659–1672 Duvall MR, Noll JD, Minn AH (2001) Phylogenetics of Paniceae (Poaceae). Amer J Bot 88:1988–1992 Frank L (1998) Análisis del sistema de ramificación del complejo Brachiaria-Urochloa (Poaceae–Paniceae), Tesis. Universidad de Buenos Aires, Buenos Aires 165 Fraser JE, Kokko G (1993) Panicle, spikelet, and floret development in orchard grass (Dactylis glomerata). Canad J Bot 71:523–532 Friedman J, Harder LD (2005) Functional associations of floret and inflorescence traits among grass species. Amer J Bot 92:1862– 1870 Gallavotti A, Zhao Q, Kyozuka J, Meeley RB, Ritter MK, Doebley JF, Pe ME, Schmidt RJ (2004) The role of barren stalk1 in the architecture of maize. Nature 432:630–635 Giraldo-Cañas D (2000) Estudios sobre la variación estructural de la sinflorescencia en el género Axonopus (Poaceae, Panicoideae, Paniceae): Tipologı́a y tendencias evolutivas. Darwiniana 38:209–218 Giussani LM, Cota-Sánchez JH, Zuloaga FO, Kellogg EA (2001) A molecular phylogeny of the grass subfamily Panicoideae (Poaceae) shows multiple origins of C4 photosynthesis. Amer J Bot 88:1935–1944 Goebel K (1931) Blütenbildung und Sproßgestaltung. 2 Erg. Bd. zur Organographie der Pflanzen. Jena. Fide Butzin (1979) Gómez-Martinez R, Culham A (2000) Phylogeny of the subfamily Panicoideae with emphasis on the tribe Paniceae: evidence from the trnL-F cpDNA region. In: Jacobs SWL, Everett J (eds) Grasses: systematics and evolution. CSIRO, Melbourne, pp 136– 140 Grass Phylogeny working Group (2001) Phylogeny and subfamilial classification of the grasses (Poaceae). Ann Missouri Bot Gard 88:373–457 Grisebach AHR (1853) Brachiaria. In: Ledebour FK (ed) Fl. Ross. Sumtibus Librariae E. Schweizerbart, Stuttgartiae, vol 4, pp 469 Henrard JT (1941) Notes on the nomenclature of some grasses. Blumea 3:411–480 Hughes DK (1923) The genus Panicum of the Flora Australiensis. Kew Bull Miscel Inform 9:305–314 Ikeda K, Sunohara H, Nagato Y (2004) Developmental course of inflorescence and spikelet in rice. Breed Sci 54:147–156 Irish EE (1998) Grass spikelets: a thorny problem. BioEssays 20:789– 793 Jacobs BF, Kingston JD, Jacobs II (1999) The origin of grassdominated ecosystems. Ann Missouri Bot Gard 86:590–643 Kellogg EA (2000) Molecular and morphological evolution in the Andropogoneae. In: Jacobs SWL, Everett J (eds) Grasses: systematics and evolution. CSIRO, Collingwood, pp 149–158 Kellogg EA, Hiser KM, Doust AN (2004) Taxonomy, phylogeny and inflorescence development of the genus Ixophorus (Panicoideae: Poaceae). Int J Pl Sci 165:1089–1105 Kunze H (1989) Probleme der Infloreszenztypologie von W. Troll Pl Syst Evol 163:187–199 Liu Q, Zhao NX, Hao G (2005) Inflorescence structures and evolution in subfamily Chloridoideae (Gramineae). Pl Syst Evol 251:183– 198 López-Ferrari AR, Espejo Serna A (2000) Nuevas combinaciones en monocotiledóneas mexicanas III (Orchidaceae, Poaceae). Acta Bot Mex 51:61–70 Malcomber ST, Preston JC, Reinheimer R, Kossuth J, Kellogg EA (2006) Developmental gene evolution and the origin of grass inflorescence diversity. Adv Bot Res 44:425–481 Maresquelle HJ (1970) Le teme évolutif des complexes d0 inflorescence. Son aptitude à suscite des problèmes nouveaux. Bull Soc bot Fr 117:1–4 Morrone O, Zuloaga FO (1991) Estudios morfológicos en el subgénero Dichanthelium de Panicum (Poaceae), con especial referencia a Panicum sabulorum. Ann Missouri Bot Gard 78:915–927 Morrone O, Zuloaga FO (1992) Revisión de las especies Sudamericanas nativas e introducidas de los géneros Brachiaria y Urochloa (Poaceae: Panicoideae: Paniceae). Darwiniana 31:43– 109 123 166 Morrone O, Zuloaga FO (1993) Sinopsis del género Urochloa (Poaceae: Panicoideae: Paniceae) para Mexico y América Central. Darwiniana 32:59–75 Morrone O, Zuloaga FO, Arriaga MO, Pozner R, Aliscioni SS (1998) Revisión sistemática y análisis cladı́stico del género Chaetium (Poaceae: Panicoideae: Paniceae). Ann Missouri Bot Gard 85:404–424 Nash G.V. (1903) Brachiaria. In: Small J.K. (ed) Flora of the Southeastern United States, pp. 80–81. New York Nelson SCH, Fernández CFJ (1998) De Xora hondurensi notulae, praecipue nomenclaturales. Fontqueria 51:3–4 Nicora EG, Rúgolo de Agrasar ZE (1987) Los géneros de gramı́neas de América Austral. Hemisferio Sur, Buenos Aires, Argentina Pensiero JF, Vegetti AC (2001) Inflorescence typology in Setaria P. Beauv. (Poaceae, Paniceae). Feddes Repert 112:371–385 Perreta M, Vegetti AC (1998) Tipologia de la inflorescencia en Leptochloa chloridiformis, Leptochloa virgata y Leptochloa mucronata (Poaceae). Kurtziana 26:135–144 Poeting R (1990) Phase change and the regulation of shoot morphogenesis in plants. Science 250:923–930 Reinheimer R (2007) Desarrollo y estructura de la inflorescencia de Brachiaria y Urochloa (Poaceae: Panicoideae: Paniceae) y sus implicancias sistemáticas. Tesis Doctoral Fac Bioq Cs Biol–UNL. Reinheimer R, Vegetti AC (2004) The inflorescence of South American species of Panicum subg. Phanopyrum sect. Laxa (Poaceae: Panicoideae:Paniceae). Beitr Biol Pflanz 73:185–199 Reinheimer R, Pozner R, Vegetti AC (2005) Inflorescence, spikelet and floral development in Panicum maximum and Urochloa plantaginea (Poaceae). Amer J Bot 92:565–575 Renvoize SA, Clayton WD (1992) Classification and evolution of the grasses. In: Chapman JP (ed) Grass evolution and domestication. Cambridge University Press, Cambridge, pp 3–37 Rua GH (1993) The synflorescence of Paspalidium rarum (Poaceae) and an alternative hypothesis about the evolution of some poaceous inflorescences. Austral Syst Bot 6:261–267 Rua GH (1996) The inflorescences of Paspalum (Poaceae, Paniceae): the Quadrifaria group and the evolutionary pathway towards the fully homogenized, truncated common type. Pl Syst Evol 201:199–209 Rua GH (1999) Inflorescencias: bases teóricas para su análisis. Sociedad Argentina de Botánica, Buenos Aires, Argentina Rua GH (2003a) Centothecoid grasses and the evolution of panicoid spikelets. Pl Syst Evol 240:83–89 Rua GH (2003b) Growth forms, branching patterns, and inflorescence structure in Digitaria sect. Trichachne (Poaceae, Paniceae). Flora 198:178–187 Rua GH, Boccaloni IB (1996) The inflorescence of Digitaria phaeotrix: morphological and developmental aspects. Flora 191:117–119 Rua GH, Weberling F (1998) Growth form and inflorescence structure of Paspalum L. (Poaceae: Paniceae): a comparative morphological approach. Beitr Biol Pflanz 69:363–431 Schmidt RJ, Ambrose BA (1998) The blooming of grass flower development. Curr Opinion Plant Biol 1:60–67 Sell Y (1976) Tendances évolutives parmi les complexes inflorescentiels. Rev Gen Bot 83:247–267 Sharp D, Simon BK (2002) AusGrass (CD ROM): grasses of Australia. CSIRO Publishing, Victoria Shaw RB, Smeins FE (1984) Additional observations of the callus in Eriochloa (Poaceae). Iselya 2:15–19 Simon BK, Jacobs SWL (2003) Megathyrsus, a new generic name for Panicum subgenus Megathyrsus. Austrobaileya 6:571–574 Soreng RJ, Davis JI (1998) Phylogenetics and character evolution in the grass family (Poaceae): simultaneous analysis of morphological and chloroplast DNA restriction site character sets. Bot Rev 64:1–84 123 R. Reinheimer, A. C. Vegetti Stapf O (1914–1932) Gramineae. In: Oliver D (ed) Flora of Tropical Africa. Lowell Reeve and Co, London, pp 1–192 Stür WW (1986) Reproductive development of the apex of Brachiaria decumbens Stapf. Ann Bot 58:569–575 Taguchi-Shiobara F, Yuan Z, Hake S, Jackson D (2001) The fascinated ear2 gene encodes a leucine-rich repeat receptor-like protein that regulates shoot meristem proliferation in maize. Genes Dev 15:2755–2766 Takahashi M, Nagasawa N, Kitano H, Nagato Y (1998) Panicle phytomer1mutations affect panicle architecture of rice. Theor Appl Genet 96:1050–1056 Thompson RA, Tyrl RJ, Estes JR (1990) Comparative anatomy of the spikelet callus of Eriochloa, Brachiaria and Urochloa (Poaceae, Paniceae, Setariineae). Amer J Bot 77:1463–1468 Torres González AM, Morton CM (2005) Molecular and morphological phylogenetic analysis of Brachiaria and Urochloa (Poaceae). Molec Phylogenet Evol 37:36–44 Trinius CB (1826) De Graminibus paniceis: Disertatio botanica altera. 125–153. Petropoli, Impendis Academiae Imperialis Scientiarum, St Petersburg Troll W (1964) Die Infloreszenzen, Typologie und Stellung im Aufbau des Vegetationskörpers 1. Gustav Fischer, Jena Troll W (1966) Botanischer Teil. In: Kommission für biologische Forschung, 110–131, Bericht. Jb. 1965. Akademie der Wissenschaften und der Literatur, Mainz Troll W (1969) Botanischer Teil. In: Kommission für biologische Forschung, 88–105, Bericht. Jb. 1968. Akademie der Wissenschaften und der Literatur, Mainz Troll W, Weberling F (1989) Infloreszenzuntersuchungen an monotelen Familien. G. Fischer, Stuttgart Tzvelev NN (1989) The system of grasses (Poaceae) and their evolution. Bot Rev 55:141–204 Vegetti AC (1987) Analisis tipológico de las inflorescencia en Paspalum (Poaceae). Kurtziana 19:155–160 Vegetti AC (1991a) Sobre politelia en las inflorescencias de Poaceae. Kurtziana 21:267–274 Vegetti A (1991b) Notes on Monotely in Poaceae inflorescences. Beitr Biol Pflanzen 66:347–350 Vegetti AC (1999) Typology of the Synflorescence of Andropogoneae (Poaceae), additional comments. Feddes Repert 110:111–126 Vegetti AC (2000) Typology of synflorescence in Oryzeae (Poaceae). Phyton (Austria) 40:71–88 Vegetti AC, Pensiero JF (1990) Inflorescence typology in Setaria poiretiana (Schultes) Kunth (Poaceae: Paniceae). Beitr Biol Pflanz 65:313–318 Vegetti AC, Anton AM (1995) Some evolution trends in the inflorescence of Poaceae. Flora 190:225–228 Vegetti AC, Pensiero JF (1999) Tipologı́a de la inflorescencia en Zizaniopsis (Oryzeae–Poaceae). Darwiniana 37:345–349 Vegetti AC, Anton AM (2000) The Grass Inflorescence. In: Jacobs SWL, Everett J (eds) Grasses: systematics and evolution. CSIRO, Melbourne, pp 29–31 Vegetti AC, Müller-Doblies D (2004) The inhibition areas within the synflorescence of Poaceae. Beitr Biol Pflanz 73:51–74 Veldkamp JF (1996a) Proposal to conserve the name Brachiaria (Trin.) Griseb. (Gramineae) with a conserved type. Taxon 45:319–320 Veldkamp JF (1996b) Brachiaria, Urochloa (Gramineae-Paniceae) in Malaysia. Blumea 41:413–437 Veldkamp JF (2004) Miscellaneous notes on mainly Southeast Asian Gramineae. Reinwardtia 12:135–140 Vollbrecht E, Reiser L, Hake S (2000) Shoot meristem size is dependent on inbred background and presence of the maize homeobox gene, knotted1. Development 127:3161–3172 Vollbrecht E, Springer PS, Goh L, Buckler Iv ES, Martienssen R (2005) Architecture of the floral branch systems in maize and related grasses. Nature 436:1119–1126 Inflorescence diversity and evolution in the PCK Clade (Poaceae) Walsh J, Freeling M (1999) The liguleless2 gene of maize functions during the transition from vegetative to reproductive shoot. Pl J 19:489–495 Watson L, Dallwitz MJ (1992) The grass genera of the world. C.A.B. International, Wallingford, UK Weberling F (1965) Typology of inflorescences. Bot J Linn Soc 59:15–221 Weberling F (1985) Aspectos modernos de la morfologı́a de las inflorescencias. Bol Soc Argent Bot 24:1–28 Weberling F (1989) Morphology of flowers and inflorescences. Cambridge University Press, Cambridge Webster RD (1987) The Australian Paniceae (Poaceae). J Cramer, Berlin and Stuttgart, Germany, pp 228–255 Webster RD (1988) General of the North American Paniceae (Poaceae: Panicoideae). Syst Bot 13:576–609 167 Zizka G (1988) Revision der Melinideae Hitchcock (Poaceae, Panicoideae). Bibl Bot 138:1–149 Zuloaga FO, Morrone O (2003) Brachiaria, Urochloa. In: Zuloaga FO, Morrone O, Davidse G, Filgueiras TS, Peterson PM, Soreng RJ, Judziewicz EJ (eds) Catalogue of new world grasses (Poaceae): III. Subfamilies Panicoideae, Aristidoideae, Arundionoideae and Danthonioideae, Contribution from the United State National Herbarium, vol 46, pp 1–662 Zuloaga FO, Morrone O, Giussani LM (2000) A cladistic analysis of the Paniceae: a preliminary approach. In: Jacobs SW, Everett J (eds) Grass: systematics and evolution. CSIRO Publishing, Collingwood, pp 123–135 123

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