Phylogenetic analyses of Spiraea (Rosaceae) distributed in the Qinghai-Tibetan Plateau and adjacent regions: insights from molecular data

摘要

The Qinghai-Tibetan Plateau (QTP) and adjacent regions comprise an excellent mountainous system to study plant diversification and speciation within East Asia. The uplift and eco-environmental processes of QTP have had an obvious effect on evolution of organisms in this region. The present study intends to test the potential correlation between evolutionary events (such as speciation and diversification) and orogenetic events (such as the intense uplift of QTP). Sequence data from five plastid DNA regions (trnL-trnF, rpl20-rpl12, rps15-ycf1, psbA-trnH, and trnS-trnG) and one nuclear ribosomal internal transcribed spacer of 19 species of the genus Spiraea L. were used in the study. Maximum parsimony and maximum likelihood trees were constructed in PAUP*, while divergence time was estimated with BEAST v1.7.5. Phylogenetic reconstruction revealed that these species form a single clade and can be divided into three sections. Diversification of Spiraea species began in middle Miocene (ca. 13.38 million years ago) during the first stage of uplifting at QTP. Diversification of Spiraea was further triggered and accelerated during the second stage of QTP uplifting in late Pliocene (ca. Last four million years). The estimated divergences time indicate that this rapid diversification was most likely triggered by the uplifting of QTP in early Pliocene, and accelerated during the Quaternary climatic oscillations.