Phylogeographic breaks within Asian butternuts indicate the existence of a phytogeographic divide in East Asia.
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 chloroplast DNA regions, one single-copy nuclear gene, and 17 nuclear microsatellite loci, supplemented with paleodistribution modeling of the major genetic clades. The genetic data consistently identified two clades, one northern, comprising Juglans mandshurica and Juglans ailantifolia, and one southern, comprising Juglans cathayensis. The two clades diverged through climate-induced vicariance of an ancestral northern range during the mid-Miocene and remained mostly separate thereafter, with geographical isolation of the Japanese Islands and refugial isolation or secondary contacts in the late Pleistocene producing further subdivision within the northern clade. But beyond all that, we also discovered a role of environmental adaptation in maintaining and/or reinforcing the north-south divergence. Asian butternuts offer a strong case for the existence of a biogeographic divide between the northern and southern parts of East Asia during the Neogene and into the Pleistocene.
State Key Laboratory of Earth Surface Processes and Resource Ecology and Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875, China.
Wei-Ning
WN
Bai
State Key Laboratory of Earth Surface Processes and Resource Ecology and Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875, China.|School of Mathematics and Computer Science, Northwest University for Nationalities, Lanzhou, 730030, China.
Wen-Ting
WT
Wang
State Key Laboratory of Earth Surface Processes and Resource Ecology and Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875, China.
Da-Yong
DY
Zhang
D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D017753:Ecosystem; D005202:Asia, Eastern; D017343:Genes, Plant; D014644:Genetic Variation; D005828:Genetics, Population; D006239:Haplotypes / Q000235:genetics; D031324:Juglans / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics; D058974:Phylogeography; D018401:Sample Size
D018742:DNA, Chloroplast
Juglans; Neogene; Quaternary; Tertiary relict flora; climate change