Regionally divergent drivers of historical diversification in the late Quaternary in a widely distributed generalist species, the common pheasant Phasianus colchicus

Historical factors such as Pleistocene climate cycles and associated environmental changes have influenced the phylogeographic structure and demographic dynamics of many species. Resulting patterns not only depend on species life-history but also vary regionally. Consequently, different populations of species with large ranges over different biomes might have experienced divergent drivers of diversification and show different population histories. Such a representative species is the common pheasant Phasianus colchicus, an ecological generalist with a wide distribution in the Palearctic and at the edge of the Oriental region. We aimed at identifying distinct phylogeographic lineages of the common pheasant and investigating their evolutionary trajectories. We used coalescent approaches to describe the phylogeographic structure and to reconstruct the spatio-temporal diversification and demographic history of the common pheasant based on a comprehensive geographic sampling of 265 individuals genotyped at seven nuclear and two mitochondrial loci. The common pheasant diversified during the late Pleistocene into eight distinct evolutionary lineages which only partly correspond to traditional morphological groups. It originated at the edge of the Qinghai-Tibetan plateau and spread from there to East and Central Asia. Only the widely distributed genetically uniform lowland lineage of East Asia showed a recent range and population expansion, starting during the last glacial. The more phylogeographic structure was found elsewhere with lineages showing no signs of recent range expansions. One lineage of subtropical south-central China is the result of long-term isolation in a climatically stable and topographically complex region. In others from arid Central Asia and China, demographic and range expansions were impeded by repeated population fragmentation during dry glacial and recent aridification. Given such a phylogeographic structure and demographic scenarios among lineages, we proposed to split the range-wide common pheasant into three species. Spatio-temporal phylogeographic frameworks of widespread species complexes such as the common pheasant provide valuable opportunities to identify regionally divergent drivers of diversification.