Memecylon batekeanum, a New Species from Southeastern Gabon, and a Note on the Circumscription of Memecylon Sect. Mouririoidea (Melastomataceae) R. Douglas Stone UC Herbarium and Department of Integrative Biology, 1001 Valley Life Sciences Building, University of California, Berkeley, California 94720-2465, U.S.A. dstone@calacademy.org; present address: Botany Department, California Academy of Sciences, 875 Howard Street, San Francisco, California 94103-3009, U.S.A. Gretchen M. Walters William L. Brown Center for Plant Genetic Resources, Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A. gretchen.walters@mobot.org Jean-Paul Ghogue Herbier National du Cameroun, B.P. 1601 Yaoundé, Cameroun. jpghogue1062@yahoo.fr ABSTRACT . Described and illustrated is Memecylon batekeanum R. D. Stone & G. M. Walters from the buffer zone of the Batéké Plateaux National Park in southeastern Gabon. This new species is closely related to M. amshoffiae Jacques-Félix of Cameroon, but is distinguished by its shrubby habit, quadrangular-alate young branchlets, fewer-flowered inflorescences, and calyptrate calyx. A provisional IUCN status of Vulnerable is assigned. Memecylon amshoffiae was treated earlier in section Mouririoidea Jacques-Félix, but this is contraindicated by evidence from ovary and anther morphology and by recent molecular phylogenetic analyses. Together, M. amshoffiae and M. batekeanum are provisionally placed next to M. diluviorum Exell in section Polyanthema Engler. RÉSUMÉ . Dans ce travail est décrit et illustré Memecylon batekeanum R. D. Stone & G. M. Walters du zone tampon du Parc National des Plateaux Batéké du Sud-est Gabon. Cette nouvelle espèce se rapproche de l’espèce Camerounaise M. amshoffiae JacquesFélix, mais s’en distingue par sa forme d’arbrisseau, ses jeunes rameaux 4-angulaires-ailés, ses cymes peu fleuries, et son calice calyptriforme. Un statut préliminaire de Vulnérable est effectué selon les critères des Listes Rouges de l’UICN. Le traitement antérieure de M. amshoffiae dans la sect. Mouririoidea Jacques-Félix est contrindiqué par des preuves obtenues à partir des caractères morphologiques des ovaires et des anthères, ainsi que par des analyses moléculaires phylogénétiques. Memecylon amshoffiae NOVON 16: 276–280. PUBLISHED ON et M. batekeanum sont provisoirement placés tous les deux près de M. diluviorum Exell dans la sect. Polyanthema Engler. Key words: Gabon, Melastomataceae, Memecylon, riverine forest, plant conservation. Regarding the widespread paleotropical genus Memecylon L., our knowledge of its diversity in Africa and Madagascar has been greatly advanced by the work of H. Jacques-Félix. His detailed morphological and anatomical studies, along with those of K. Bremer, have led to the recognition of the segregate genera Spathandra Guillemin & Perrottet, Lijndenia Zollinger & Moritzi, and Warneckea Gilg (Jacques-Félix, 1978b; Bremer, 1982)—concepts that have received additional support from molecular phylogenetic analyses (Stone, 2006). Within Memecylon s. str., Jacques-Félix (1978a, 1979) accounted for the western and central African taxa by recognizing section Polyanthema Engler (ca. 16 species) and by proposing two new sections, Afzeliana Jacques-Félix (ca. 18 species) and Mouririoidea Jacques-Félix (5 species). The first two groups have unilocular ovaries and are diagnosed by the shape of the fruit (globose in sect. Polyanthema vs. ellipsoid to oblong in sect. Afzeliana). Section Mouririoidea is characterized by a 4-loculed ovary and conspicuously 4-lobed calyx; it is an especially distinctive group in which Jacques-Félix (1978a, 1979, 1983a, b) placed M. lateriflorum (G. Don) 26 JULY 2006. Volume 16, Number 2 2006 Stone et al. Memecylon batekeanum from Gabon 277 Figure 1. Flower of Memecylon amshoffiae Jacques-Félix (ca. 10 times natural size) showing the enlarged and elongated anther connectives, each bearing a dorsal gland. The four separate petals are recurved at anthesis and the bases overlap one another, the corolla thus falsely appearing sympetalous. Photograph by RDS on left bank of Nyong River ca. 10 km southwest of Eséka, South province, Cameroon, corresponding to the specimen Stone & Ghogue 2529 (CAS, YA). Bremekamp (the type species of the section) along with M. amshoffiae Jacques-Félix, M. mouririoides Jacques-Félix, M. occultum Jacques-Félix, and M. ramosum Jacques-Félix. Recent phylogenetic analyses of nuclear genomic sequences have demonstrated that Memecylon amshoffiae, a riparian forest tree from Cameroon’s South province, is quite divergent from M. lateriflorum and other members of section Mouririoidea (Stone, 2004 & unpublished data). Furthermore, although JacquesFélix (1979) described the ovary of M. amshoffiae as 4-loculed, this is clearly incorrect: the ovary is unilocular, based on new dissections by the first author of flower buds from an isotype specimen (Leeuwenberg 5142, UC) and another recent collection from the type region (Stone & Ghogue 2529, CAS). Memecylon amshoffiae also has elongated anther connectives, such that the gland is positioned on the dorsal surface (Fig. 1), while in M. lateriflorum and other members of section Mouririoidea the connectives are scarcely or not prolonged, the gland thus positioned laterally on the face opposite the anther sacs (Jacques-Félix, 1979, 1983a). These morphologi- cal and molecular results provide strong indication that M. amshoffiae must be excluded from the circumscription of section Mouririoidea. The current infrageneric placement of M. amshoffiae is discussed following the description of a new, closely related species from southeastern Gabon. Memecylon batekeanum R. D. Stone & G. M. Walters, sp. nov. TYPE: Gabon. Haut Ogooué: buffer zone of Batéké Plateaux National Park, embarquiadère to Projet Protection des Gorilles, 1u589170S, 14u009340E, 400 m, 25 Nov. 2001, G. Walters, A. Bradley, G. Nang-Essouma & A. Mbaniboua 967 (holotype, MO; isotypes, CAS, LBV, WAG). Figure 2. Haec species M. amshoffiae Jacques-Félix affinis, sed ab eo habitu fruticoso, ramulis juvenibus quadrangulari-alatis, inflorescentia breviore pauciflora semel ramificante atque calyce calyptriformi differt. Evergreen shrub less than 1 m high; young branchlets quadrangular and narrowly alate (this condition evidently not persisting below the first 278 Novon Figure 2. Memecylon batekeanum R. D. Stone & G. M. Walters. —A. Flowering branch. —B. Inflorescence with calyptrate calyx. —C. Flower with three petals removed. —D. Petal. —E. Anther, frontal view. —F. Anther, lateral view. —G. Leaf, abaxial surface. —H. Leaf, adaxial surface. Drawn from the holotype Walters et al. 967 (MO). internode); internodes mostly 3–5 cm long. Leaves thinly coriaceous, dark green and somewhat shining above, dull and much paler below (drying brown); petioles 3–4 mm long; blades elliptic, (5.6–)6.5–8.0 (–8.5) 6 (2.9–)3.1–3.8(–4.1) cm, cuneate at base, rounded and then abruptly acuminate at the apex; acumen slender, mostly 1.2–1.6 cm long, often curved; mid-nerve finely impressed on the upper surface, prominent on the lower surface; transverse nerves scarcely visible, faintly impressed on the upper surface in dried material, obscure on the lower surface, 12 to 14 pairs oriented at slightly oblique angles relative to the mid-nerve and closely spaced (2–5 mm) relative to one another; lateral nerves situated , 1 mm from the margin, scarcely visible. Cymes 1–1.5 cm long, geminate or solitary in the axils Volume 16, Number 2 2006 (rarely at older nodes below the current leaves or at bracteolate nodes alternating with those bearing fully developed leaves), 1- to 2(to 3)-flowered, with terminal flower usually absent; peduncles 2–5 mm long; primary axes (2.5–)3–5 mm long; secondary axes lacking; bracts deciduous, not seen. Flowers with pedicels 0.5–1 mm long; hypantho-calyx with thick texture, subglobose in bud, ca. 4.5 mm long, 3.5– 4 mm diam., apex conical and apiculate; calyx in bud entirely covering the corolla, calyptrate and falling off neatly (or remaining attached to one side) at anthesis leaving a truncate margin (the margin occasionally provided with 4 V-shaped sinuses ca. 1 mm deep); hypantho-calyx at anthesis broadly campanulate, 2.5– 3 6 5 mm; petals lilac, ca. 4–4.5 6 4.5–5 mm, broadly ovate to suborbicular, apiculate, the midnerve keeled on the abaxial surface; anthers 2 6 1 mm; connective yellow, broadly saddle-shaped by the gland that occupies nearly the entire length on the dorsal side; filaments ca. 2.5 mm long; epigynous chamber with 8 parietal partitions and 8 interstitial lines; style robust, 4 mm long; ovary unilocular; ovules 12. Fruits not seen. The epithet batekeanum refers to the type locality and to the Batéké people who live in this region. The rolling hills of the Batéké Plateaux, which extend well into the adjacent Republic of Congo, are formed of Kalahari sands, which are the deepest sand deposits in the world (Haddon et al., 2000). Annual rainfall does not exceed 1600 mm and occurs in two seasons of October to December and February to May. Vegetation cover is a mosaic of grassland maintained by anthropogenic fire and forest confined to the moist river valleys (Koechlin, 1961). The savanna is heavily populated by Hymenocardia acida Tulasne (Euphorbiaceae) and Annona senegalensis Persoon (Annonaceae), and is often dominated by Ctenium newtonii Hackel (Poaceae) and other graminoid and Cyperaceae species including Schizachyrium thollonii (Franchet) Stapf (Poaceae), Loudetia simplex (Nees) C. E. Hubbard (Poaceae), and Rhynchospora candida (Nees) C. B. Clarke (Cyperaceae). The adjacent forest contains many common species of the GuineoCongolian region (sensu Monod, 1957; White, 1983), including Anonidium mannii (Oliver) Engler & Diels (Annonaceae), Uapaca paludosa Aubréville & Leandri (Euphorbiaceae), Santiria trimera (Oliver) Aubréville (Burseraceae), and Pentaclethra macrophylla Bentham (Fabaceae). Other Melastomataceae species occurring in the understory include Memecylon aff. sitanum Jacques-Félix, M. occultum, Spathandra blakeoides (G. Don) Jacques-Félix, and the riverine Dichaetanthera strigosa (Cogniaux) Jacques-Félix. The sandy substrate and fire regime do not seem to Stone et al. Memecylon batekeanum from Gabon 279 contribute to plant endemism in the area, as psammophytes are abundant and pyrophytes are nearly absent in the flora. The Guineo-Congolian forest species present in the area are evidently shared with a larger forested block to the north and west; however, there are minor floristic influences from the Sudano–Zambesian region (Walters et al., 2006). Although Memecylon batekeanum is common at its type locality, the species is currently known from a single flowering collection. It may well be a localized endemic with an Area of Occupancy (AO) of perhaps no more than 10 km2. It is furthermore found within the buffer zone of the Batéké Plateaux National Park, where the riverine forest is most likely kept in check by anthropogenic fire. This combination of factors suggests a provisional conservation status of Vulnerable (VU D2), as defined by the IUCN (2001). The new species closely resembles Memecylon amshoffiae of Cameroon, especially in its leaf morphology and texture, color of the leaves on drying, axillary inflorescences, and size and texture of the hypantho-calyx. The petals and anthers of the two taxa are identical in both morphology and color; even their ecology is similar (riverine forest). In addition, they are resolved as sister taxa in molecular phylogenetic trees, and they share an unusual, 82-base repeat in the ITS2 region of nuclear ribosomal DNA (Stone, 2004). In both species, the corolla in bud is entirely concealed by the calyx (an unusual feature in Memecylon). However, whereas in M. amshoffiae the calyx separates at anthesis into four valvate lobes with intervening sinuses 2–3 mm deep, in M. batekeanum the calyx is calyptrate and falls off neatly leaving a truncate margin (occasionally with 4 shallow indentations). The new species also differs in its shrubby habit, quadrangular-alate young branchlets, and shorter, fewer-flowered cymes (1–1.5 cm long and mostly 1- to 2-flowered vs. generally 2–3.5 cm long and 3- to 7-flowered in M. amshoffiae). The ranges in length of the peduncle, the primary inflorescence axes, and the pedicels overlap in the two species, although in M. batekeanum these measurements are usually less. Furthermore, the cymes of M. amshoffiae often have secondary branches, whereas in M. batekeanum these are evidently absent. Other subtle differences are found in the leaf dimensions; in M. batekeanum the blades are somewhat shorter relative to their width (mostly less than 2.5 times longer than wide vs. greater than 2.5 times longer than wide in M. amshoffiae), the apex is more abruptly acuminate, and the acumen is more slender. In addition, the known populations of the two species are isolated from each other by a distance of about 700 kilometers. Together, Memecylon amshoffiae and M. batekeanum appear closely related to yet another riparian 280 Novon species, M. diluviorum Exell, which ranges from Angola (Cabinda, the type region) to Gabon (see Jacques-Félix, 1983b, and recent collections at CAS and MO). However, M. diluviorum notably differs from the M. amshoffiae–M. batekeanum species pair in that the corolla in bud is well exposed by the truncate calyx, which at anthesis becomes evenly parted into four segments with intervening, V-shaped sinuses ca. 1.5 mm deep. Jacques-Félix (1983b) previously treated M. diluviorum in section Polyanthema, and both M. amshoffiae and M. batekeanum are provisionally placed in this section (Stone, 2004). An additional Gabonese collection that is obviously allied with Memecylon amshoffiae and M. batekeanum was made in Ogooué-Maritime (or Nyanga?) province, 32 km north of Igotchi-Mouenda (12 May 1997, G. McPherson 16950, CAS). This specimen, taken from a tree 7 m high, is distinguished mainly by its calyx, which ruptures irregularly and eventually falls off leaving a very thick and sinuately 4-lobed margin (vs. valvately 4-lobed in M. amshoffiae, calyptrate in M. batekeanum). McPherson 16950 may represent yet another new (albeit closely related) species, which would not be very surprising given the prevalence of regional and local endemism in African Memecylon. illustration and Roy Gereau for consultation on the Latin diagnosis. Acknowledgments. The authors are grateful to Frans Breteler and Angela Martins for their reviews of an earlier version of this paper. RDS thanks Isabelle Tavares of the UC herbarium for financial support of his mission in Cameroon from March to May 2003, and Gaston Achoundong, head of the National Herbarium of Cameroon, for logistical support of same. James Solomon, the curator of the Missouri Botanical Garden herbarium, granted a loan and gift of conventional specimens as well as access to material in that institution’s DNA Bank for molecular phylogenetic studies. GMW thanks Ginot NangEssouma of the National Herbarium of Gabon for field assistance and Liz Pearson and Alphonse Mbaniboua of the Projet Protection des Gorilles for logistical support. John Myers is thanked for the fine Literature Cited Bremer, K. 1982. Lijndenia, a re-established paleotropical genus of the Melastomataceae–Memecyleae. Nordic J. Bot. 2: 121–124. Haddon, I. G. 2000. Kalahari group sediments. Pp. 173–181 in T. C. Partridge & R. R. Maud (editors), The Cenozoic of Southern Africa. Oxford Monographs on Geology and Geophysics, Vol. 40. IUCN. 2001. IUCN Red List Categories and Criteria Version 3.1. Prepared by the IUCN Species Survival Commission. IUCN, Gland, Switzerland. Jacques-Félix, H. 1978a. Les subdivisions du genre Memecylon (Melastomataceae) en Afrique. Adansonia, ser. 2, 17: 415–424. ———. 1978b. Les genres de Memecyleae (Melastomataceae) en Afrique, Madagascar et Mascareignes. Adansonia, ser. 2, 18: 221–235. ———. 1979. Espèces nouvelles et peu connues du genre Memecylon (Melastomataceae) en Afrique. Adansonia, ser. 2, 18: 409–432. ———. 1983a. Mélastomatacées. In: B. Satabié & J.-F. Leroy (editors), Flore du Cameroun 24: 1–181. Délégation Générale à la Recherche Scientifique et Technique, Yaoundé. ———. 1983b. Mélastomatacées. In: J.-F. Villiers (editor), Flore du Gabon 25: 1–168. Muséum National d’Histoire Naturelle, Laboratoire de Phanérogamie, Paris. Koechlin, J. 1961. La Végétation des Savanes dans le Sud de la République du Congo (Capitale Brazzaville). ORSTOM, Montpellier, France. Monod, T. 1957. Les Grandes Divisions Chorologiques de l’Afrique. Comité consultatif tropical africain/Conseil scientifique pour l’Afrique, Publ. no. 24, London. Stone, R. D. 2004. Phylogenetic Systematics of Melastomataceae, Subfamily Olisbeoideae. Ph.D. Dissertation, University of California, Berkeley. ———. 2006. Phylogeny of major lineages in Melastomataceae, subfamily Olisbeoideae: Utility of nuclear glyceraldehyde 3-phosphate dehydrogenase (GapC) gene sequences. Syst. Bot. 31: 107–121. Walters, G., A. Bradley & R. Niangadouma. 2006. Floristic affinities of Gabon’s Batéké Plateaux: Guineo-Congolian plants on Kalahari sands. Pp. 259–266 in S. A. Ghazanfar & H. J. Beentje (editors), Taxonomy and Ecology of African Plants, Their Conservation and Sustainable Use. Royal Botanic Gardens, Kew. White, F. 1983. Vegetation of Africa: A Descriptive Memoir to Accompany the UNESCO/AETFAT/UNSO Vegetation Map of Africa. UNESCO, Paris.