Oral Paper

         Systematics

Phylogenetic systematics of Vigna sensu stricto (Leguminosae, Fabaceae): the Old World Vigna

Presenting Author
Ashley Egan
Description
Premise of study: The evolutionary relationships between the diverse Vigna Savi species have been through many taxonomic revisions in legume systematics to reflect natural groupings. Vigna includes economic crop and wild species that sustain much of the world. Previous revisions to taxonomic organization of Vigna s.s. have presented questions about the Old World (OW) Vigna interspecific and inter-subgeneric relationships. • Methods: A molecular phylogenetic analysis was undertaken to resolve long-standing OW Vigna taxonomic questions. Maximum likelihood and Bayesian phylogenetic analyses included cpDNA matK-trnK and nuclear ribosomal ITS/5.8S (ITS) sequence variation. African species were comprehensively sampled within the context of New World (NW) relatives and genera within Phaseolinae. • Key results: The matK and ITS data analyses concurred in resolving five well-supported clades of Vigna s.s.: subg. Lasiospron, a reduced subg. Vigna, subg. Haydonia, subg. Ceratotropis, an enlarged subg. Plectrotropis, and a clade including V. kirkii and V. stenophylla that could be considered as new subgenus or section. • Conclusions: Former subg. Vigna is reduced to yellow and blue flowered species and subg. Plectrotropis is enlarged to all white-pink-purple flowered species. Vigna s.s. in the Americas now includes subg. Lasiospron and a few pantropical species. Elaborate floral asymmetries are readily used to apomorphically diagnose nearly all the American genera. The age estimates of the extant diversification of the American and its Old World sister clade are approximately coeval at ca. 6 – 7 million yr.