Abstract:

Although much research has focused on biodiversity in mountain regions, elevational patterns of community similarity (i.e. species turnover) and the underlying processes are still rarely discussed. In this study, based on field investigations of 28 forest communities in the western Qinling Mountains, we evaluated the combined effects of habitat divergence and geographical distance on patterns of similarity in species composition using Mantel tests and multiple regressions on distance matrices (MRM). We also compared the rates of similarity decay of different life forms with geographical distance using permutation tests. Results indicated that, for all three life forms, community similarity decreased significantly with elevational, geographical, and habitat distances. Geographical distance and habitat heterogeneity together explained 41.1%, 59.0% and 47.4% of variance in species composition of trees, shrubs and herbs, respectively, with geographical distance uniformly explaining more variance than habitat heterogeneity. Woody plants showed a faster decay in similarity with geographical distance than herbaceous species. These results suggest that, at the scale of our study, dispersal limitations and habitat filtering influence species composition together, and highlighted that dispersal limitation may play a more important role in structuring the forest communities of the western Qinling Mountains.

Key words: dispersal limitation, habitat filtering, habitat heterogeneity, elevational gradient, community assembly, species turnover