NEW COMBINATIONS IN MADAGASCAN VANGUERIEAE ( RUBIACEAE ) FOR THE GENERA PSYDRAX , PYROSTRIA , AND RYTIGYNIA

The paucity of taxonomic and nomenclatural works on Madagascan Rubiaceae, particularly compared to mainland Africa, is evident by the large number of epithets for species residing in genera that are either not in current usage or have been circumscribed so as to exclude them. In this contribution we take the opportunity to make 12 new combinations in the tribe Vanguerieae Dumort., for the genera Psydrax Gaertn. (7 spp.), Pyrostria Comm. ex A. Juss. (3 spp.), and Rytigynia Blume (2 spp.). Vanguerieae is a robust monophyletic group placed within subfamily Ixoroideae (Andreasen & Bremer, 2000; Persson, 2000), which can be characterized by the following morphological features: inflorescence always axillary; flowers with secondary pollen presentation; corolla lobes valvate in bud; pollen presenters distinct (cylindrical, coroniform or mitriform, mostly recessed (hollow) with style attached within, or not recessed and style attached at the base); ovary 2–10(–12)-locular, the ovules solitary and pendulous; fruit with (1–)2–10 pyrenes; pyrenes cartilaginous to strongly woody with apical pre-formed germination slits; seeds with oily endosperm and relatively large embryos; radicle superior (Bridson & Verdcourt, 1998). This contribution is a precursor (De Block, 2005; Rakotonasolo & Davis, 2006) to a checklist of the Rubiaceae of Madagascar and Comoros (Davis et al., in prep.).


INTRODUCTION
The paucity of taxonomic and nomenclatural works on Madagascan Rubiaceae, particularly compared to mainland Africa, is evident by the large number of epithets for species residing in genera that are either not in current usage or have been circumscribed so as to exclude them.In this contribution we take the opportunity to make 12 new combinations in the tribe Vanguerieae Dumort., for the genera Psydrax Gaertn.(7 spp.), Pyrostria Comm.ex A. Juss.(3 spp.), and Rytigynia Blume (2 spp.).
This contribution is a precursor (De Block, 2005;Rakotonasolo & Davis, 2006) to a checklist of the Rubiaceae of Madagascar and Comoros (Davis et al., in prep.).

NEW COMBINATIONS IN PSYDRAX
Psydrax is a genus found throughout the Old World tropics from Africa, throughout southern and SE Asia, to Australia (Bridson, 1985).The circumscription of this genus presents few problems and species are easily assigned to it.A few salient characters allow for easy identification within Vanguerieae, including: leaves usually subcoriaceous to coriaceous (although chartaceous and deciduous in three African species); inflorescences various, basically cymose but also umbellate (by reduction of inflorescence branches), or fasciculate (by reduction of the peduncle), occasionally few-flowered, or rarely solitary; calyx limb consisting of a dentate to repand rim, usually much shorter than the disk; style long and slender, usually long-emergent; pollen presenter cylindrical, always longer than wide, hollow from the base to the middle, apex bifid or rarely deeply cleft; anthers usually reflexed; pyrene cartilaginous to woody, often bullate, with a shallow apical crest; and embryo with cotyledons set parallel to the ventral face of the seed (Verdcourt & Bridson, 1991;Bridson & Verdcourt, 1998).The monophyly of Psydrax is supported by molecular evidence (Lantz & Bremer, 2004).
For most of its nomenclatural history Psydrax was considered to be a synonym of Canthium Lam.Apart from some confusing and erroneous usage of Psydrax in Madagascar in the19th century (for details see Bridson, 1985: 688-689), Capuron (1969) was the first to suggest that many species from Africa, Madagascar and Asia should be moved from Canthium to Psydrax, although he did not propose any combinations.According to Bridson (1985: 689) Capuron's concept of Psydrax included the African genus Keetia E. Phillips and was wider than the current circumscription.Cavaco (1966Cavaco ( , 1967aCavaco ( , 1967bCavaco ( , 1968Cavaco ( , 1969Cavaco ( , 1971Cavaco ( , 1972) ) published a series of papers on Madagascan Vanguerieae but did not take up the proposed reinstatement of Psydrax by Capuron (1969).Commenting on the last of his series (Cavaco, 1972), which detailed new species of Canthium and Rytigynia, Bridson (1985: 689) stated that: "It can be assumed from his descriptions and illustrations that species 13-19 [Canthium], as numbered in the text, could well be accommodated in Psydrax but none of these species has been seen by me".Type specimens of these seven species of Canthium (C.Pyrostria is a genus of 37 species ('World Checklist of Rubiaceae': www.rbgkew.org.uk/wcsp/rubiaceae), which is distributed in Africa, the Seychelles, Madagascar, and the Mascarenes (Bridson & Verdcourt, 1998) and probably extends to south and SE Asia (Bridson, 1987;Davis & Ruhsam, 2005).The circumscription is relatively straightforward (Bridson, 1987) and species can be succinctly characterized by the possession of the following characters: inflorescences entirely enclosed in bud by paired connate persistent bracts (with silky hairs inside); inflorescences umbellate or 1-flowered (typical of female flowers); leaves usually with obscure tertiary venation; pollen presenter solid with style attached at the base; corolla throat densely congested with hairs (Bridson & Verdcourt, 1998).Depending on the species the flowers are either hermaphrodite or unisexual and the ovaries 2-or several-locular.The circumscription of Pyrostria and its monophyly is supported by molecular data (Lantz & Bremer, 2004).Lantz & Bremer (2004) have suggested that other Madagascan Canthium, which lack distinct paired bracts (e.g.see Bridson, 1987 for Groups III-V & Canthium subg.Bullockia) may need to be included in Pyrostria, although this would disrupt the present morphological circumscription of the genus.Between 1966and 1971, Cavaco (1966, 1967a, 1967b, 1968, 1969, 1971) described many new species of Pyrostria (usually 2-locular species) and Pseudopeponidium (very similar to Pyrostria; usually pluri-locular species).According to Bridson (1987: 623) Cavaco's generic concepts became confused in the last paper of his series (Cavaco, 1972), and she notes: "Although no specimens from species block 20-25 [Canthium] of his 1972 paper are represented at Kew, the descriptions suggest they could have been placed in Pyrostria [as opposed to Canthium]".Material of these six species has now been seen by us and we can confirm the placement of three species in Pyrostria.These placements conform with the circumscription of the genus after Bridson (1987), including the presence of distinct paired bracts.The other three Canthium species in species block 20-25 (Cavaco, 1972) do not have all the salient characters of Pyrostria but may well belong in the genus; further study is required.
After this contribution, there are c.20 species of Madagascan Canthium remaining, which are similar to Pyrostria (see above) but lack distinct paired bracts.Further work is needed to ascertain whether these taxa (as well as a number of endemic Vanguerieae genera; see Davis & Bridson, 2003a, 2003b) should be included in Pyrostria (Lantz, 2003).Canthium s.s.does not occur in Madagascar but is restricted to Africa and Asia (Bridson, 1992;Lantz & Bremer, 2004).
Pyrostria isomonensis (Cavaco) A.P. Davis & Govaerts, comb. nov.Basionym: Canthium isomonense Cavaco (1972) (Bridson & Verdcourt, 1998: 285).Five entries were needed for Rytigynia in Bridson's key to the genera of Vanguerieae in 'Flora Zambesiaca' (Bridson & Verdcourt, 1998), for example.Even though the eastern African species were revised by Verdcourt (1987), the generic concept (after Robyns, 1928) was not seriously challenged.Typically the inflorescence is few-flowered; most species have pluri-locular ovaries, but some are 2-locular; several species have long, and often conspicuous, corolla lobe appendages but other do not.Many species have tufts of hair inside the stipules.A few species have linear calyx lobes and some taxa are spiny.Recent molecular and morphological studies by Lantz (2003) and Lantz & Bremer (2004, 2005) show that the genus is not monophyletic.Most Rytigynia species fall within a well-supported monophyletic group that includes Fadogia Schweinf., the Fadogia-Rytigynia group (Lantz & Bremer, 2005), which as a general rule can be distinguished from closely related taxa (e.g.Vangueria) by the presence of domatia and a calyx usually with poorly developed calyx lobes, although this rule is not without exceptions (Lantz & Bremer, 2005).Species of Rytigynia from Madagascar (Lantz & Bremer, 2005) fall within the Fadogia-Rytigynia group, and have the long corolla lobe appendages, which are characteristic of many Rytigynia species.
As Rytigynia predates the publication of Fadogia, possible taxonomic changes would still see these species being placed in Rytigynia, rather than Fadogia.Two species of Madagascan Vanguerieae, namely Canthium erythroxyloides Baill.and Pyrostria syringifolia (Baker) Hochr., possess the characters of the central core of Rytigynia and of the Fadogia-Rytigynia group (Lantz & Bremer, 2005).
To further bring the nomenclature of Malagasy Vanguerieae in accordance with current usage, we propose two new combinations.
ankotekonense Cavaco, C. austro-orientale Cavaco, C. bathieanum Cavaco, C. esirense Cavaco, C. manambyanum Cavaco, C. occidentale Cavaco, C. sambiranense Cavaco) have now been examined by us and we are left in no doubt that they belong to Psydrax.New combinations for the above seven species are required and are proposed below.Psydrax ankotekonensis (Cavaco) A.P.Davis & Bridson, comb.nov.