Oeceoclades beravensis (Rchb. f.) R. Bone & Buerki

Bone, Ruth E., Sanz, Ernesto & Buerki, Sven, 2014, The transfer of Eulophia beravensis Rchb. f. to Oeceoclades Lindl., a genus with its centre of diversity in Madagascar (Eulophiinae, Orchidaceae), Candollea 69 (2), pp. 201-205 : 202-203

Oeceoclades beravensis (Rchb. f.) R. Bone & Buerki , comb. nova.

Ξ Eulophia beravensis Rchb. f. in Bot. Zeitung (Berlin): 39: 449. 1881.

Ξ Graphorkis beravensis (Rchb. f.) Kuntze , Revis. Gen. Pl. 2: 662. 1891.

Ξ Lissochilus beravensis (Rchb. f.) H. Perrier in Humbert, Fl. Madagascar Comores 49(2): 42. 1941.

Typus: MADAGASCAR. Prov. Mahajanga: Beravi , VII. 1879, Hildebrandt 3055 (holo-: W [ W-Rchb.Orch.0010 984 ] image seen; iso-: BM [ BM000525715 ]!, GOET [ GOET008578 ] image seen, K [ K000410344 ]!; M [ M0103 484 ] image seen, P [ P000108 614 ]!).

Habitat and Ecology. – Oeceoclades beravensis has a broad distribution in the sub-humid to sub-arid areas of Madagascar to the west and south, where it grows in sandy soils, often forming dense stands in the understorey of western dry forest and wooded grassland-bushland mosaic (sensu MOAT & SMITH, 2007) ( Fig. 2 ).

Conservation status. – Oeceoclades beravensis is currently considered to be endemic to Madagascar, where it is widespread. The vegetation types that it occupies are threatened, however. The wooded grassland-bushland mosaic, generally considered to be a secondary vegetation type (MOAT & SMITH, 2007; although see BOND & al., 2008 for alternative views on grassland origins) is disturbed by cattle grazing, clearance for fuelwood and human mediated fires (MOAT & SMITH, 2007). The western dry forest is targeted for charcoal and fuelwood and, according to MOAT AND SMITH (2007), is being cleared at a faster rate than any other forest type in Madagascar. Based on 40 collections from several herbaria (BM, K, MO and P; acronyms follow THIERS, 2014) an “Extent of Occurrence” of 397,139 km 2, an “Area of Occupancy” (AOO) of 360 km 2 and 39 subpopulations (calculation following CALLMANDER & al., 2007), including six in the Protected Area network (Andranomena, Ankarafantsika, Ankarana, Baie de Baly, Namoroka, and Zombisty), O. beravensis is assigned a preliminary status of “Near Threatened” [NT] following IUCN Red List Categories and Criteria ( IUCN, 2012). Under the “B” Criteria, based solely on EOO, this species would be categorized as “Least Concern”, however it occurs in vegetation that is threatened by land use change (see above) and we adopt a precautionary approach as recommended by the Red List Guidelines ( IUCN, 2014). The specimens used for the assessment are included on the “ Eulophiinae Scratchpad ” ( BONE, 2014).

Observations. – Eulophia beravensis is morphologically unique among all Malagasy Eulophiinae taxa, including Oeceoclades , by having cane like stems that form large clumps or dense stands in scrub and forest understorey. Like the xerophytic Eulophia species E . leachii A. V. Hall (from Southern Africa) and E. petersii (Rchb. f.) Rchb. f. (a widespread species across dryland Africa and extending into the Arabian Peninsula; WCSP, 2014) the leaves of E. beravensis have minutely serrate margins ( Fig. 3 ). They are, however, narrow and coriaceous, unlike these Eulophia species , that have somewhat fleshy almost succulent leaves. These morphological traits (that appear to be adaptations to arid and sub-arid environments) are clearly shown to have evolved independently based on unpublished molecular data produced by the authors, with all three taxa belonging to separate lineages.

The affinity of a species of Eulophia from Mozambique ( E. biloba Schltr. ), that was not sampled by the authors, should be investigated to determine whether it is conspecific with Oeceoclades beravensis (P. J. CRIBB, pers. comm.). If this is found to be the case, the validity of our comb. novae would be maintained since it bears the older basionym. The conservation assessment would require revision, however, to take into account a broader geographical distribution that would encompass Mozambique.

Figures

Fig. 2. – Distribution map of Oeceoclades beravensis (Rchb. f.) R. Bone & Buerki (stars), based on herbarium specimens mapped on the bioclimatic zones of Madagascar (after CORNET, 1974; see SCHATZ, 2000). Protected areas are highlighted in grey.

Fig. 3. – Oeceoclades beravensis (Rchb. f.) R. Bone & Buerki (near Ihosy airport, Fianarantsoa Prov. in 1996). [Photo: J. Hermans]