Dynamics of small-mammal communities along an elevational gradient

Elevation is one of the most important natural gradients that is strongly shaping communities across relatively small areas. However, few studies have followed the temporal dynamics of elevational patterns, even in organisms for which population and community fluctuations have been extensively studied, such as rodents. Here we report the multiannual dynamics of small-mammal communities along an elevational gradient in the Southern Carpathians. During a 5-year survey, we conducted live-trapping in forested and shrubby habitats, at elevations between 820 and 2040 m. We used partial constrained multivariate analysis and mixed-effects models to test the effect of elevation, year, and their interaction. Community metrics differed significantly between even and odd years and temporal changes had stronger effect on small-mammal communities than elevation. The 2-year pattern of dynamics was especially marked in the yellow-necked field mouse (Apodemus flavicollis (Melchior, 1834)). Species abundance was predicted not only by year and elevation, but also by their interaction. The dominant rodent species, the bank vole (Myodes glareolus (Schreber, 1780)) and A. flavicollis, showed opposite annual patterns in relation to elevation, possibly as a strategy to avoid competition. Failure to consider the fluctuations in montane small-mammal communities may lead to wrong assessment of species' state and distribution.