|Systematics of the genus Derris Lour. (Fabaceae) and its closely related genera in Thailand
Y. Sirichamorn, F.A.C.B. Adema & P.C. van Welzen
Netherlands Centre for Biodiversity Naturalis (section NHN), Leiden University,
P.O. Box 9514, 2300 RA Leiden, The Netherlands
Abstract─ Derris-like plants are members of the tribe Millettieae of the Fabaceae (Leguminosae-Papilionoidae). The plants are morphologically similar and classified informally by their geographic distribution as palaeotropic Derris and neotropic Derris. In Thailand, only the palaeotropic Derris occurs and it consists of Derris in the strict sense (including Brachypterum), Paraderris, and the basal millettioid genus Aganope. The revision of Thai species shows that in total 24 Thai species (Aganope 3; Derris 17 and Paraderris 4) can be recognised. Three species, D. pseudomarginata from south-eastern, D. glabra from southern peninsular and Derris sp. (not named yet) from central-northern, will be newly described. The classic morphological studies clearly support the separation of the three genera. However, the genus Paraderris is reunited within Derris s.str. in a morphology-based phylogenetic tree. Preliminary results of phylogenetic analyses based on 2 molecular chloroplast markers, trnL-F and psba-trnH, also support the exclusion of the genus Aganope from other Derris-like genera of the old world. And again, Paraderris (and also Brachypterum) are reunited within Derris s.str., but with low boostrap supports. One species, P. laotica, should be excluded from the other species of Paraderris due to its morphological and molocular similarity to Derris. Two other molecular markers, nuclear ITS and cloroplast trnK-matK, are still being processed including more species of Derris-like plants to provide an exact delimitation and phylogeny of Derris and its closely related genera in the very near future.
Key words─ Aganope, Derris, Fabaceae, Millettieae, Paraderris, Thailand.