What drives the species richness patterns of non-volant small mammals along a subtropical elevational gradient?


Q. Yang, Key Lab of Zoological Systematics and Evolution, Inst. of Zoology, Chinese Academy of Sciences, CN–100101 Beijing, PR China. E-mail: yangqs@ioz.ac.cn


The biodiversity of non-volant small mammals along an extensive subtropical elevational gradient was studied for the first time on Gongga Mountain, the highest mountain in Hengduan Mountain ranges in China, located in one of the 25 global biodiversity hotspots. Non-volant small mammals were replicate sampled in two seasons at eight sampling sites between 1000 and 4200 m elevation on the eastern slope of Gongga Mountain. In all, 726 individual small mammals representing 25 species were documented in 28 800 trap nights. The species richness pattern for non-volant small mammals along the elevational gradients was hump-shaped with highest richness at mid-elevations. However, different richness patterns emerged between endemic and non-endemic species, between larger-ranged and smaller-ranged species and between rodents and insectivores. Temperature, precipitation, plant species richness and geometric constraints (mid- domain effect) were most significant in explaining species richness patterns. Based on the analysis of simple ordinary least squares (OLS) and stepwise multiple regressions, the overall richness pattern, as well as the pattern of insectivores, endemic species and larger-ranged species showed strong correlation with geometric constraint predictions. However, non-endemic species richness was more strongly correlated with temperature, while rodent richness was correlated with plant species richness. Our study shows that no single key factor can explain all richness patterns of non-volant small mammals. We need to be cautious in summarizing a general richness pattern of large species groups (e.g. small mammals or mammals) from species in smaller groups having different ecological distributions and life histories. Elevational richness patterns and their driving factors for small mammals are more likely dependent on what kind of species we study.