A synoptic revision of Brexia (Celastraceae) in Madagascar George E. SCHATZ Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299 (USA) [email protected] Porter P. LOWRY II Missouri Botanical Garden, P.O. Box 299, St. Louis, MO 63166-0299 (USA) [email protected] and Département Systématique et Évolution, Muséum national d’Histoire naturelle, CP 39, 57 rue Cuvier, F-75231 Paris cedex 05 (France) [email protected] ABSTRACT A taxonomic revision of the genus Brexia Noronha ex Thouars (Celastraceae) KEY WORDS in Madagascar is presented. Reevaluation of morphological characters allows Celastraceae, the recognition of 11 species, three of which are described as new. Pre- Brexia, Madagascar, liminary conservation assessments of each species are calculated according to conservation. IUCN Red List criteria. RÉSUMÉ Révision synoptique de Brexia (Celastraceae) à Madagascar. Une révision taxonomique du genre Brexia Noronha ex Thouars MOTS CLÉS (Celastraceae) à Madagascar est présentée. La réévaluation de divers caractères Celastraceae, morphologiques permet de reconnaître 11 espèces dont trois sont nouvelles et Brexia, Madagascar, décrites ici. Une analyse préliminaire du statut de conservation pour chaque conservation. espèce est effectuée selon les critères des Listes Rouges de l’UICN. INTRODUCTION been placed in or near Celastraceae, Escallo- niaceae, Grossulariaceae, Hydrangeaceae, The genus Brexia Noronha ex Thouars has Saxifragaceae, or Brexiaceae, either on its own, or engendered considerable debate among workers including Ixerba from New Zealand and Roussea with respect to family placement, relationships, from Mauritius (see KOONTZ & SOLTIS 1999 for and species delimitation. At various times it has a complete history of family placement and ADANSONIA, sér. 3 • 2004 • 26 (1) : 67-81 © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. 67 Schatz G.E. & Lowry II P.P. relationships). Similarly, while some authors have branched cymose inflorescences occur in B. cour- considered Brexia to be monotypic (CAPURON in siana, B. decurrens, and B. marioniae. In addition, herb.; VERDCOURT 1968), others have recognized inflorescences may be solitary and axillary as many as nine (PERRIER DE LA BÂTHIE 1942), or (B. alaticarpa, B. apoda, B. australis, B. humbertii, even 10 (LEROY 1968) species. Recent molecular B. madagascariensis, B. montana), or they may be phylogenetic studies have now definitively clustered and borne on the main stem (cauliflory) resolved the placement of Brexia in Celastraceae- (B. cauliflora, B. coursiana, B. decurrens, B. mario- Celastrales, and shown that it is unrelated to both niae). Among the species with pseudo-umbellate Ixerba (Ixerbaceae-Crossosomatales) and Roussea inflorescences, B. humbertii is easily recognized (Rousseaceae-Asterales) (KOONTZ & SOLTIS by its large, persistent bracts subtending the flow- 1999; SIMMONS et al. 2001; APG II 2003). Here ers, whereas B. australis is distinguished by its we reconsider species delimitation within reduced inflorescences with one or two flowers Malagasy Brexia as part of a survey of Madagascar and a short peduncle. eastern littoral forests, as well as part of a study to The form of the disc varies more or less consis- identify priority areas for plant conservation. tently among species of Brexia. Referred to by Reevaluation of all material of Brexia at the PERRIER DE LA BÂTHIE (1933, 1942) as “lames principal herbaria holding Malagasy collections pétaloïdes”, “languettes”, or “dents”, the disc seg- (K, MO, P, TAN, and TEF) was conducted in ments alternate with the stamens and are usually order to reassess the diagnostic species-delimiting fused at their base to the lower part of the fila- characters proposed by PERRIER DE LA BÂTHIE ments. The disc segments are petaloid and entire (1942). In particular, inflorescence characteris- in B. alaticarpa, whereas in B. marioniae they are tics, flower size, and the form of the disc were petaloid, entire (or rarely very shallowly 2-3- confirmed as taxonomically important features, lobed) and keeled on the inner surface, and in as well as the margins of adult leaves. Although B. australis they are irregularly, shallowly to not yet documented in all members of the genus, deeply, 4-8-laciniate. it is likely that the margins of leaves on juvenile The following taxonomic framework recog- and sucker shoots (“gourmands”) in most, if not nizes 11 species of Brexia in Madagascar, 10 of all, species are regularly or at least sometimes which are endemic, and one of which (B. mada- spinose, as is most commonly encountered in gascariensis) also occurs in the Comoro Islands, B. madagascariensis. Margins of adult leaves vary and along the eastern coast of Africa in among species and sometimes within species; Mozambique, Tanzania, and Zanzibar (VERD- they can be consistently entire (B. alaticarpa, COURT 1968). Although not treated here, we pre- B. arborea, B. madagascariensis), usually entire or fer to recognize the upland form of Brexia on the rarely subentire (B. cauliflora, B. marioniae), both Seychelles as a distinct species, B. microcarpa Tul., entire/subentire and distinctly spinose (B. apoda, rather than as a subspecies of B. madagascariensis B. coursiana, B. humbertii), or consistently spin- (e.g., by FRIEDMANN 1994). Within Madagascar, ose (B. australis, B. decurrens, B. montana). morphological variation among species of Brexia The basic inflorescence of Brexia is a cyme, is well correlated with eco-geographic parameters, which, however, has been modified and/or including bioclimate (CORNET 1974; SCHATZ reduced to appear essentially unbranched and 2000, 2001; see also LOWRY et al. 1997, 1998) pseudo-umbellate in B. apoda, B. australis, and geological substrate (DU PUY & MOAT B. humbertii, B. madagascariensis and B. mon- 1996). Preliminary conservation assessments have tana. In B. alaticarpa and B. cauliflora, the sec- been assigned according to IUCN (2001), and ondary branches of the inflorescence are very are based primarily on Extent of Occurrence short, with branching only near the apex of the (EO), Area of Occupancy (AO), number of peduncle, and thus the inflorescence appears localities/subpopulations, and projected decline corymbiform. In B. arborea, and occasionally in relation to presence/absence in protected areas. B. apoda, the peduncle is essentially absent, For the Material examined cited below under resulting in sessile, fasciculate flowers. Distinctly each species, abbreviations are as follows: FC, 68 ADANSONIA, sér. 3 • 2004 • 26 (1) Revision of Brexia (Celastraceae) in Madagascar Forêt Classée; PN, Parc National; RNI, Réserve (http://www.mobot.org/MOBOT/research/mada Naturelle Intégrale; RS, Réserve Spéciale; and gascar/gazetteer/). STF, Station Forestière. A full listing of exsiccatae for each species, with complete localities and lati- tude/longitude coordinates, is available through BREXIA Noronha ex Thouars W3 TROPICOS (http://mobot.mobot.org/ W3T/Search/vast.html). Images of selected taxa Gen. Nov. Madag.: 20 (1806), nom. cons. are also available on the Web at (http:// www.mobot.org/MOBOT/Madagasc/celast.html). TYPE. — Brexia madagascariensis (Lam.) Ker Gawl. Geographic coordinates indicated in square brackets were assigned post facto using available Venana Lam., Tabl. Encycl. Méth. Bot. 2: t. 131 (1792). — Type: V. madagascariensis Lam. information on Malagasy place names and Thomassetia Hemsl. in Hook. Ic. Pl. 28: t. 2736 topographic maps, compiled as a gazetteer of (1902). — Type: T. seychellarum Hemsl. (= B. micro- botanical collecting localities in Madagascar carpa Tul.). Key to the species of Brexia in Madagascar 1. Inflorescences borne among the leaves ...................................................................................................... 2 1’. Inflorescences borne on woody stems or trunk (cauliflory) ........................................................................ 9 2. Inflorescences sessile to subsessile fascicles or borne on a short peduncle < 2 cm long ................................ 3 2’. Inflorescences borne on a distinct peduncle > 2 cm long .......................................................................... 5 3. Inflorescences 2-flowered or sometimes reduced to a single flower; adult leaves often subsessile, occasionally petiole 1-7 mm long, largest blades not exceeding 12 cm long .............................................. 4. B. australis 3’. Inflorescences 2-15-flowered; adult leaves with a distinct petiole > 10 mm long, blades at least 13 cm long .... 4 4. Inflorescences axillary, sessile to short pedunculate, often bearing small bracts at the apex of the peduncle; petaloid disc segments deeply linear-lobed ................................................................................ 2. B. apoda 4’. Inflorescences mostly cauliflorous, rarely axillary, usually a cluster of 2 or more peduncles lacking apical bracts; petaloid disc segments entire or rarely shallowly lobed .......................................... 10. B. marioniae 5. Inflorescences pseudo-umbels, the peduncles unbranched ........................................................................ 6 5’. Inflorescences small corymbs or cymes, the peduncles usually branched .................................................. 8 6. Peduncles with 1-2 distinct, persistent bracts at the apex subtending the pseudo-umbel...... 8. B. humbertii 6’. Peduncles lacking persistent apical bracts .................................................................................................