How Does the Phasianidae Maintain Its Diversity in Central China?

The hypothesis of allopatric speciation suggests that spatial separation is the major driver to speciation. The ecological niche theory suggests that differentiations in niche dimensions allow more species to co-exist in ecological communities. It is thus predicted that, (1) species from the same genus will tend to appear in different ecological communities due to the strong force of exclusion between them; (2) sibling genera may co-occur in communities without direct spatial associations (i.e., with indirect spatial associations); and (3) when they are directly associated, the genera will be different in some ecological features to avoid resource competitions. In this study, we used infrared camera trap data and statistic techniques to set up species association networks in four national nature reserves (NNRs) in central China, and the data of mitochondrial cytochrome b (cytb) gene sequences downloaded from the National Center for Biotechnology Information (NCBI) database to test the predictions based on the phasianids (order Galliformes) appearing in the networks. We found 14 phasianid species belonging to 12 genera, resulting in 91 potential species pairs and 45 potential genus pairs. A total of 12 associations were identified between species, accounting for 13.2% of the potential species pairs; and 11 associations identified between genera, accounting for 24.4% of the potential genus pairs. The chi-square goodness-of-fit test results showed that the spatial separation existed extensively between the phasianids at levels of species (86.8% of potential species pairs) and genera (75.6% of potential genus pairs). There were 2 genera each containing 2 species; i.e., the Crossoptilon (containing the white-eared pheasant C. crossoptilon and the blue-eared pheasant C. auritum) and the Chrysolophus (the golden pheasant C. pictus and the Lady Amherst's pheasant C. amherstiae). These congeneric species appeared in different ecological communities. The other 10 genera each contained only one species in community, although they have more species in taxonomy. This monotypicalness in community makes them effectively avoid competition within genera. The Spearman rank-order correlation coefficient tests showed no general correlation between the phylogenetic distance and the spatial association coefficient of the genera of Phasianidae, but the correlation existed in Liancheng, which may be attributed to the difference in evolutionary history between Palearctic and Indomalayan realms. Discussions suggested that the genus pairs of Tetraophasis-Ithaginis and Ithaginis-Crossoptilon are associated in a way that is consistent with beneficial interactions. The genera in symmetric associations may differentiate in diets. It is thus concluded that the spatial separation may play a major role in promoting and maintaining the diversity of Phasianidae, and the differentiation in ecological features play a supplementary role.