A Molecular Phylogeny and New Infrageneric Classification ofMucunaAdans. (Leguminosae-Papilionoideae) including Insights from Morphology and Hypotheses about Biogeography

Abstract

Premise of research. The genus Mucuna has a pantropical distribution and comprises approximately 105 species, many of which show great economic value for forage, ornament, and medicine. To date, phylogenetic relationships within Mucuna have not been investigated using molecular data. The aim of this study was to build a phylogenetic framework for Mucuna to address questions about its monophyly, infrageneric relationships, divergence times, and biogeography.Methodology. We sequenced plastid (trnL-F) and nuclear ribosomal (internal transcribed spacer) regions and applied Bayesian and maximum likelihood analyses. An ancestral area reconstruction coupled with a divergence time analysis was used to investigate the historical biogeography of the genus.Pivotal results. Our results show that Mucuna is a monophyletic genus and that subgenus Stizolobium is a monophyletic group within it. We present here the analyses and results that support the need to recircumscribe subgenus Mucuna and to segregate a small group of species with large fruits into a newly proposed subgenus (to be described formally elsewhere after additional investigations).Conclusions. On the basis of ancestral area reconstruction and divergence time analyses, we conclude that the genus Mucuna originated and first diversified in the Paleotropics around 29.2 Ma and achieved a pantropical distribution through multiple long-distance dispersal events, which were facilitated by the occurrence of seeds adapted to oceanic dispersal.