Taxonomy and phylogeny of the genus Crotalaria (Fabaceae): An overview

Crotalaria (Fabaceae) is the largest legume genus represented by 81 species in India. The existing sectional classification for Crotalaria in India is based on morphological characters and is not completely supported by the molecular phylogenetic studies. Molecular systematic studies of the Indian sections Crotalaria and Calycinae have enabled merging of both these sections into Calycinae. Trifoliolate condition in the genus and leaf beak not spirally twisted are plesiomorphies for the genus. Pollen morphology is a poor criterion for infrageneric classification since pollen grains do not show much variability. Chromosome counts for the genus show two basic numbers which are x=7 and predominantly x=8. Polyploidy is common in the many new world species. Crotalaria from the new world seems to be the last colonized and polyploidy is one of the evolutionary strategies for diversification in the New World species. Molecular phylogenetic studies suggest that the sections Calycinae and Crotalaria are non-monophyletic. The genus Crotalaria with 81 species, consisting of 27 endemics (confined to peninsular India) indicates an ongoing rapid evolution and diversification.