A Dispersal and Vicariance Analysis of the Genus Caragana Fabr.

The genus Caragana Fabr., consisting of approximately 70 species, has a temperate Asian distribution and occurs mainly in the drought and cold regions of the northwestern and southwestern Tibetan Plateau of China. The distribution pattern of the genus was investigated using dispersal-vicariance analysis (DIVA). The results indicate that vicariance versus dispersal plays a major role in the evolution of the genus and that short-distance dispersal also exists. There is no fossil record of this genus. Therefore,Caragana is inferred as an advanced taxon in terms of its limited temperate Asian distribution. Based on the morphological variation and ecological adaptation in Caragana, the generic speciation is postulated to be related to the uplifting of the Tibetan Plateau and to the increasing arid conditions of Central Asian lands since the Neogene. The Mongolian Plateau and the Tibetan Plateau are hypothesized as the barriers of vicariance between East Asia and western Central Asia.