Phylogeography of <italic>Eomecon chionantha</italic> in subtropical China: the dual roles of the Nanling Mountains as a glacial refugium and a dispersal corridor.

Background: Mountains have not only provided refuge for species, but also offered dispersal corridors during the Neogene and Quaternary global climate changes. Compared with a plethora of studies on the refuge role of China’s mountain ranges, their dispersal corridor role has received little attention in plant phylogeographic studies. Using phylogeographic data of <italic>Eomecon chionantha</italic> Hance (Papaveraceae), this study explicitly tested whether the Nanling Mountains, which spans from west to east for more than 1000 km in subtropical China, could have functioned as a dispersal corridor during the late Quaternary in addition to a glacial refugium. Results: Our analyses revealed a range-wide lack of phylogeographic structure in <italic>E. chionantha</italic> across three kinds of molecular markers [two chloroplast intergenic spacers, nuclear ribosomal internal transcribed spacer (nrITS), and six nuclear microsatellite loci]. Demographic inferences based on chloroplast and nrITS sequences indicated that <italic>E. chionantha</italic> could have experienced a strong postglacial range expansion between 6000 and 1000 years ago. Species distribution modelling showed that the Nanling Mountains and the eastern Yungui Plateau were the glacial refugia of <italic>E. chionantha</italic>. Reconstruction of dispersal corridors indicated that the Nanling Mountains also have acted as a corridor of population connectivity for <italic>E. chionantha</italic> during the late Quaternary. Conclusions: Our results suggest that the Nanling Mountains may acted dual roles as a dispersal corridor in east-west direction and as a glacial refugium in subtropical China during the late Quaternary. The population connectivity mediated by the mountain range and a strong postglacial range expansion are the most likely reasons for the lack of phylogeographic structure in <italic>E. chionantha.</italic> The hypothesis of dual roles of the mountain range presented here sheds new insights into the phylogeographic patterns of organisms in subtropical China. [ABSTRACT FROM AUTHOR]