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
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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
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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).
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