Phylogeny of palaeotropic Derris‐like taxa (Fabaceae) based on chloroplast and nuclear DNA sequences shows reorganization of (infra)generic classifications is needed

Abstract

Palaeotropic Derris-like taxa (family Fabaceae, tribe Millettieae) comprise 6-9 genera. They are well known as important sources of rotenone toxin, which are used as organic insecticide and fish poison. However, their phylogenetic relationships and classification are still problematic due to insufficient sampling and high morphological variability. Fifty species of palaeotropic Derris-like taxa were sampled, which is more than in former studies. Three chloroplast genes (trnK-matK, trnL-F IGS, and psbA-trnH IGS) and nuclear ribosomal ITS /5.8S were analyzed using parsimony and Bayesian methods. Parsimony and Bayesian analyses of individual and combined markers show more or less similar tree topologies (only varying in terminal branches). The old-world monophyletic genera Aganope, Brachypterum, and Leptoderris are distinct from Derris s.s., and their generic status is here confirmed. Aganope may be classified into two or three subgeneric taxa. Paraderris has to be included in Derris s.s. to form a monophyletic group. The genera Philenoptera, Deguelia, and Lonchocarpus are monophyletic and distinct from each other and clearly separate from Derris s.s. Morphologically highly similar species of Derris s.s. are shown to be unrelated. Our study shows that previous infrageneric classifications of Derris are incorrect. Paraderris elliptica may contain several cryptic lineages that need further investigation. The concept of the genus Derris s.s. should be reorganized with a new generic circumscription by including Paraderris but excluding Brachypterum. Synapomorphic morphological features will be examined in future studies, and the status of the newly defined Derris and its closely related taxa will be formalized.