Introduction
The Vitaceae of Madagascar and the Comoro Islands were last treated by Descoings (1967) in the “Flore de Madagascar series”. In the course of evaluating the species diversity of Cissus for the Catalogue of Vascular Plants of Madagascar (Madagascar Catalogue, 2011), Cissus glossopetala f. oblongifolia Desc. stood out as a highly distinctive entity from the typical C. glossopetala (Baker) Suess. In addition to obvious morphological differentiation, the two taxa have geographically distinct ranges. Cissus glossopetala is restricted to littoral and humid forests from sea level to ca. 100 m and is distributed along the north and east coast of Madagascar and in the Comoros Islands. Cissus glossopetala f. oblongifolia occurs in mid-elevation humid forests in central and southeastern Madagascar. Given the morphological and ecological differentiation, we believe C. glossopetala f. oblongifolia deserves recognition at the rank of species. The new combination based on C. glossopetala f. oblongifolia is not available (the name C. oblongifolia Merr. has been validly published for a species from the Philippines), therefore, we propose the new name C. decaryiWahlert & Phillipson, dedicated to Raymond Decary (1891–1973), collector of the type. Because C. decaryi is only known from two collections, we hope that recognizing this taxon as a full species will bring attention to it, in an effort to identify new populations.
Key to separate Cissus decaryi from C. glossopetala
1. Leaf deltoid or suborbicular, base cordate to truncate, 5–10 cm long (excluding basal lobes and acumen), 6–13.5 cm wide; petiole 2–6.5 cm long C. glossopetala
1a. Leaf lanceolate or oblong, base cuneate or truncate, 3–7 cm long (excluding acumen), 1–2.5 cm wide; petiole 0.8–1.2 cm long C. decaryi
Taxonomy and nomenclature
Cissus decaryi Wahlert & Phillipson, nom. et stat. nova
≡ Cissus glossopetala f. oblongifolia Desc. in Bull. Soc. Bot. France 113: 93. 1966.
Typus: MADAGASCAR. Prov. Toliara: Col du Tsitonga — barika [Tsitongambarika], district de Fort-Dauphin, 600 m, [24°39′S 47°03′E], 9.IX.1932, fl., Decary 10597 (holo-: P [P00061294]!; iso-: P [P00061295]!).
Conservation status. — Cissus decaryi is restricted to midelevation humid forests from ca. 500–600 m, in Toliara and Fianarantsoa provinces. It is only known from two specimens and was last collected in 1932. The type specimen is located in the newly proclaimed Forêt de Tsitongambarika Category VI Protected Area (IUCN, 2011), however recent intensive fieldwork at this site has not revealed any new material and the species is clearly very rare at this locality. The other specimen (Perrier de la Bâthie 4498) was collected in the vicinity of Vatovavy Mountain, Fianarantsoa Prov. in 1911. The forests on Vatovavy are highly fragmented and degraded and it is very likely that C. decaryi no longer exists there. It is possible that it could be present in nearby Ranomafana National Park, although it has never been found at this relatively wellcollected site. With an estimated AOO of 18 km2 only two known subpopulations, one occurring in a protected area (Tsitongambarika) but not collected since 1932, but with the other inferred to been severely reduced, and with further reduction expected, or even possibly extinct, and is therefore assigned a preliminary status of “Critically Endangered” (CR A2ac; D) following IUCN Red List Categories and Criteria (IUCN, 2001) (calculations following Callmander & al., 2007).
Acknowledgements
We are grateful to the curators of the herbaria in G, P, MO, TAN and TEF, for providing access to their collections, and to our colleagues Martin Callmander and George Schatz for decisions on the conservation status of the new species. The authors were supported by grants from the U.S. National Science Foundation (0743355) and the Andrew W. Mellon Foundation.
