A phylogeny of Onobrychis and its relationships with allied genera of Hedysareae.

Results about a phylogenetic analysis of the genus Onobrychis Mill., tribe Hedysareae, DC. are presented. The systematic knowledge of tribe Hedysareae is still incomplete, with difficult circumscription of genera and species. Analyses were undertaken using both nuclear (ITS) and chloroplast (matK) markers for a set of 78 accessions covering 41 Onobrychis species, besides previously sequenced Hedysareae accessions. The phylogenetic methods used were maximum parsimony, maximum likelihood, and Bayesian analyses to produce phylogenetic trees and robustness indices. The genus Onobrychis was resolved as paraphyletic, with species of the genera Eversmannia Bunge and Hedysarum L. nested within it. The position of the section Membranacea of genus Hedysarum was as a sister group to Onobrychis and Eversmannia, separated from other accessions of Hedysarum. Variation in the 2 markers was sufficient to resolve infrageneric groups in Onobrychis and Hedysarum, but we were unable to completely resolve certain species in Onobrychis, particularly those within the sect. Onobrychis. The cause of this difficult species delimitation may be related to recent speciation, hybridization, and introgression events, particularly between cultivated species and their wild relatives, and the presence of cryptospecies as suggested by intraspecific polyploid series.