A Revision of the Malagasy Endemic Talinella (Portulacaceae)
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A revision of the Malagasy endemic Talinella (Portulacaceae) Wendy L. APPLEQUIST Missouri Botanical Garden, P.O. Box 299, St Louis, MO 63166-0299 (USA) [email protected] ABSTRACT A revision is presented of the genus Talinella Baill. Twelve species are recog- nized, of which seven ( T. albidiflora, T. ankaranensis, T. bosseri, T. humbertii, KEY WORDS Portulacaceae, T. latifolia, T. tsitondroinensis, T. xerophila) are newly described. Talinella Talinella, grevei Danguy is divided into four subspecies, of which two (subsp. calcicola, Madagascar, subsp. hirsuta) are newly described and one (subsp. sarmentosa) is newly conservation, endemism, recognized at that taxonomic level. All species are endemic to Madagascar, new species. and most are vulnerable or endangered. RÉSUMÉ Révision du genre endémique malgache Talinella (Portulacaceae). Une révision du genre Talinella Baill. est présentée. Douze espèces sont reconnues, dont sept sont nouvelles ( T. albidiflora, T. ankaranensis, T. bosseri, MOTS CLÉS Portulacaceae, T. humbertii, T. latifolia, T. tsitondroinensis, T. xerophila). Talinella grevei Talinella, Danguy est divisée en quatre sous-espèces, dont deux sont nouvelles (subsp. Madagascar, calcicola, subsp. hirsuta) et une est nouvellement reconnue comme sous- conservation, endémisme, espèce (subsp. sarmentosa). Toutes les espèces sont endémiques à Madagascar nouvelles espèces. et la plupart sont menacées. INTRODUCTION T HOMSON & B RUNET 1990; S AKAI & W ELLER 1999). Talinella is the only genus of Portu- The Malagasy endemic genus Talinella Baill. lacaceae endemic to Madagascar ( Dendro- differs from most Portulacaceae in being woody portulaca Eggli being properly placed in and usually dioecious with a usually fleshy fruit, a Amaranthaceae and congeneric with Deeringia suite of characters that are positively associated R.Br.; A PPLEQUIST & P RATT in press). As and that occur with unusual frequency in plants described by BAILLON (1886) it contained only endemic to island habitats (e.g., C ARLQUIST the type species, T. boiviniana Baill.; two more 1974; B AWA 1980; L LOYD 1985) for reasons that, species were published by SCOTT E LLIOT (1891) though much discussed, remain unclear (e.g., and D ANGUY (1915). L EANDRI (1962) described B AWA 1980; G IVNISH 1980; DONOGHUE 1989; another as a new genus, Sabouraea Leandri, ADANSONIA, sér. 3 • 2005 • 27 (1) : 47-80 47 © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. Applequist W.L. which he tentatively referred to Flacourtiaceae; several previously unrecognized species and sub- later (LEANDRI 1965), he recognized its syno- species; this suggests that the current range of the nymy with Talinella but failed to make the nec- genus may be the remnants of an original distrib- essary transfer. Talinella was most recently revised ution spanning most of the drier portions of the by EGGLI (1997), who recognized five species. country. Talinella is restricted to the more arid Talinella was originally placed in Portulacaceae habitats, including dry forest, bush and transi- when described by BAILLON (1886). P AX & tional scrub; no species have been found in the H OFFMAN (1934) considered this placement eastern humid forest. Substrates include sand, doubtful, as did M C N EILL (1974), and the genus calcite and granite; individual taxa are frequently was not included in C AROLIN’s (1987, 1993) restricted to a single substrate. cladistic analysis and classifications of Specimen locality data for all species of Tali- Portulacaceae. N YANANYO (1986, 1990) argued nella have been analyzed to provide preliminary in favor of the placement of Talinella within estimates of conservation status according to the Portulacaceae and eventually within the tribe IUCN Red List Categories and Criteria (IUCN Talineae Fenzl, whereas H ERSHKOVITZ (1993) 2001). Most species are of limited range, and sev- suggested a closer relationship to Portulacaria eral are known from only a single collection or a Jacq. and Ceraria Pearson & Stephens. handful of sites. It is likely that most of these N YANANYO ’s position is strongly supported by species are indeed uncommon. Some of the recent molecular data, which indicate that recorded localities are reasonably accessible, and Talinella is embedded within a paraphyletic collections would probably be more numerous if Talinum Adans. (HERSHKOVITZ & Z IMMER 1997; the species in the central part of the country were A PPLEQUIST & W ALLACE 2001). common. Moreover, most of these localities are Recent herbarium and field observations sug- not situated within Madagascar’s network of pro- gested that the subset of existing collections made tected areas; some collections have been made available on loan to E GGLI were inadequate to from degraded bush, and others from areas where portray the true range and distribution of varia- further environmental damage has occured since tion within Talinella. As a result, four of the five the time of collection. Based on estimates using species now recognized (EGGLI 1997) were rather specimen data alone, six of the 12 species recog- broadly defined and most were apparently wide- nized may be provisionally classified as vulnerable spread, but included morphologically distin- and one as critically endangered, while an eighth guishable disjunct populations that were is lacking data but is likely to be vulnerable or individually of very limited range and thus of endangered. Although T. grevei is widespread, potential conservation concern. For this paper, as two distinctive subspecies are known from a very a contribution to a treatment of Portulacaceae of limited number of collections and may also be of Madagascar and Comoros, the collections at P, conservation concern. MO, TAN and TEF were examined. Twelve species of Talinella are recognized herein, of M ORPHOLOGY which seven are described as new. Morphological variation in Talinella is complex; within groups of very similar and perhaps G EOGRAPHY AND CONSERVATION recently diverging species, there are few fixed Talinella can be roughly described as having a character discontinuities, making delimitation of disjunct distribution, with one group of species species boundaries difficult. In the most broadly confined to the extreme northern end of Mada- distributed and best-collected species, T. grevei gascar and another concentrated in the arid Danguy, infraspecific variability is as great as that southern region, from Toliara on the southwest- usually seen among closely related species. ern coast to Fort-Dauphin at the extreme south- However, where morphological differences are east. Isolated specimens from central and accompanied by significant discontinuity in geo- northwestern localities, previously identified as graphic range, habitat, and/or substrate prefer- outlying populations of existing species, represent ence, recognition at the species level may be 48 ADANSONIA, sér. 3 • 2005 • 27 (1) Revision of Talinella (Portulacaceae) considered appropriate even where material is nal or lateral. The distalmost branches, which are limited. Geographical and substrate data may usually subtended by small triangular bracts, are thus play a useful role in identification. frequently reduced, so that the terminal branches are tipped and the flowers subtended by small V EGETATIVE CHARACTERS clusters of empty bracts or (especially in T. grevei The habit of almost all species of Talinella is and its apparent relatives) by clusters of bracts and that of a shrub with lax, sarmentose or lianoid small buds. Variation in bud size may to some ex- branches. Talinella pachypoda Eggli may be erect tent reflect sequential maturation, although in with a single main stem and a swollen basal T. grevei a comparison of budding, flowering and caudex; T. grevei may have a very short basal fruiting inflorescences suggests that many of the trunk of over 20 cm in diameter. Individuals of smaller buds do not mature. A distinction may be such species as T. grevei and T. boiviniana Baill., made between species that have numerous flowers especially where commingled with lianas or other open simultaneously (e.g., T. grevei, T. boiviniana) plants, can present the appearance of a liana and species with few mature flowers, but inflores- growing on another shrub. Label information cence size is quite variable within some species and may be misleading in this regard, as a complex even within individuals of those species, thus habit is easily misinterpreted by collectors; several species cannot be neatly separated by the number species that have been described as lianoid proba- of flowers per inflorescence. bly rarely if ever are in the technical sense. Coloration, size and number of the bracts vary Lenticels may be present or absent on older among species. In some species, bud scales are twigs, varying even within individuals. Some sometimes seen in the axils of leaf scars at the base species (e.g., T. boiviniana, T. ankaranensis) are of the peduncle and the distal portion of the sup- consistently glabrous, but most species some- porting twig. These scales are usually small, dark times or usually bear papillae on the smaller and inconspicuous, but in some of the species with twigs. Papillae may be entirely white and occa- white and brown twig papillae, especially T. hum- sionally elongated into short cilia, as in T. grevei bertii Appleq., they may be over 1mm long, re- and related species, or they may be intermingled curved and multicolored with a pale apex, giving white and brown, as in T. pachypoda, T. dauphi- the appearance