Montane small mammals are subjected to strong forces of dispersal limitation and habitat filtering that mainly operate on their community structures along the altitudinal direction. However, so far little is known about the relative contributions of dispersal and niche processes to their community assembly. By applying the newly-proposed PER-SIMPER/DNCI (dispersal–niche continuum index) framework to small mammal occurrence data collected from 21 extensive altitudinal gradients, we quantitatively assess the relative importance of dispersal and niche processes on mammalian community assembly in a large mountainous region of southwest China. We compared the pairwise DNCI values among assemblages from low, middle, and high altitudinal zones and overall DNCI values between glires and insectivores that differ in dispersal abilities to test three explicit (altitudinal connectivity, environmental difference, and dispersal ability) hypotheses. The overall DNCI values for all small mammal species combined (-12.7 ± 0.4, 90 species), glires (-12.8 ± 0.5, 56 species) and insectivores (-13.5 ± 1.4, 34 species) values were all negative, while insectivores showed a lower value than glires. For both all species combined and glires, we found a lower pairwise DNCI value between the low and high altitudinal zones than that between the other two pairs of altitudinal zones. Our study indicated that altitudinal dispersal process dominates the taxonomic composition of small mammal assemblages in this region. Importantly, the results reinforced the idea that community structures of less vagile taxa are more subjected to dispersal limitation, yet another idea that assemblages from further altitudinal areas are more differentiated by dispersal process was only supported in glires and all species combined. Community biologists should therefore pay attention to recent climate-induced upward range shifts by montane species, which may dramatically alter their community structures in different altitudinal zones through dynamics of immigration and mountaintop extinction.

This dataset is an integrated one based on montane small mammal trapping data collected between 1981 and 2018 in the mountainous region of southwest China. Small mammals including glires (mammals belonging to the orders of Rodentia and Lagomorpha) and insectivores (order Eulipotyphla) were surveyed based on consistent sampling techniques (line transects, quadrats and trap nights) along 21 elevational gradients.