The Nanling Mountains of southern China played a variable role as a barrier and refuge for birds depending upon landscape structure and timing of events

The Nanling Mountains, an important mountain range and watershed in south China, harbor a wealth of relictual plant species, and are considered a ‘museum' of subtropical biodiversity. With respect to birds, however, the roles of the Nanling Mountains in impeding the dispersal of the subtropical birds and, as a result, shaping their population and community structures have received little consideration. To examine these roles, we compiled and analyzed two datasets. 1) To test the mountains' influence on gene flow, we undertook a comparative phylogeographic study comparing mitochondrial COI and Cytb DNA sequences of five sylvioid resident bird species of the mountains (Huet's fulvetta Alcippe hueti, red-billed leiothrix Leiothrix lutea, greater necklaced laughingthrush Pterorhinus pectoralis, Indochinese yuhina Staphida torqueola and mountain bulbul Ixos mcclellandii). 2) To examine differential community development over the history of modern birds, we examined distributional data of all species of the Nanling region using public species occurrence records. For part 1), we sampled 327 individuals from 36 sites and conducted correlation analysis of genetic and geographic distances, taking into account the landscape of the mountains. We found that the mountains do not seriously impede gene flow among populations but influenced species differently. For part 2), comparative analysis of 446 species in 81 families indicated that family membership influenced the community composition of birds in Nanling region. Variation in family distributions is attributable to both environmental and evolutionary factors. Overall, we found that the Nanling Mountains are not currently a substantial barrier to gene flow among the species we studied but act as a corridor and refuge for these birds. However, analyses on higher ranked community data suggest the mountains acted as a barrier in older times, corresponding to the known diversification events in southeast Asian avifauna.