Phylogeographic breaks within Asian butternuts indicate the existence of a phytogeographic divide in East Asia

Summary East Asia has been hypothesized to be subdivided into two distinct northern and southern areas, separated by a band of dry climate that was far more severe in the early Tertiary but still exists today. However, this biogeographic hypothesis has rarely been tested using a molecular phylogeographic approach. We genotyped 70 populations throughout the distributional range of Asian butternuts ( Juglans section Cardiocaryon ) using eight...