Molecular Phylogeny and Divergence Time Estimation of Onobrychis sect. Onobrychis (Fabaceae) based on nrDNA ITS

Phylogenetic analysis and estimating divergence time of O. sect. Onobrychis were conducted using nrDNA ITS sequence data. A total of 60 species from the section Onobrychis, seven species of the five sister sections belonging to O. subgen. Sisyrosema and eight species of other genera of the tribe Hedysareae (Eversmannia subspinosa ، Greuteria argyreum، Corethrodendron multijugum ، Taverniera cuneifolia، Hedysarum polybotrys، Sulla spinosissima و Alhagi maurorum) as outgroups were chosen. Phylogenetic analyses were performed by maximum likelihood and Bayesian methods. The results showed that O. sect. Onobrychis is monophyletic and composed of two main well-supported clades. The first clade includes annual and perennial species with long wings, often with the basic chromosome number x= 8. The second clade comprises perennial species with short wings and two annuals with long wings, having the basic chromosome number x= 7. Sect. The divergence time estimation of this section was analyzed with BEAST. The section was originated at 11.96 Mya in middle Miocene and subsequently diverged into two linages at 9.29-9.58 Mya.