Evolutionary response to the Qinghai-Tibetan Plateau uplift: Phylogeny and biogeography of Ammopiptanthus and tribe Thermopsideae (Fabaceae)

Based on sequence data from the nuclear ITS and four cpDNA regions ( matK , trnH-psbA , trnL-trnF , rbcL ), phylogeny of the tribe Thermopsideae was inferred. Our analyses supported this tribe being merged into a monophyletic Sophoreae in a broad sense, with exclusion of Pickeringia . Genera of Sophoreae were separated into the Thermopsoid clade and Sophoroid clade. Monophyly of Anagyris , Baptisia and Piptanthus were basically supported in the Thermopsoid clade. Ammopiptanthus , consisting of A. mongolicus and A. nanus , nested within the Sophoroid clade, with Salweenia as its sister. Ammopiptanthus and Salweenia disjunctively distributed in desert of Northwestern China and Hengduan Mountains, respectively. Divergence age was estimated based on the ITS phylogenetic analysis. Emergence of the common ancestor of Ammopiptanthus and Salweenia , divergence between these two genera, and split of Ammopiptanthus species occurred at approximately 26.96 Ma, 4.74 Ma and 2.04 Ma, respectively, which may be response to the second, third, fourth rapid uplift of the Qinghai-Tibetan Plateau, respectively.