Species richness and distribution of non-volant small mammals along an elevational gradient on a Mediterranean mountain

We explored the alpha and gamma patterns in species richness of non-volant small mammals on Mt. Snežnik (sea level: 1796 m) on the northern edge of the Mediterranean Basin. A total of 2871 individuals were sampled belonging to 23 different species of rodents and soricomorphs. Two estimates of true species richness (sample-based rarefaction and abundance-based coverage estimator of species richness, ACE) yielded very similar values to empirical data. The empirical number of species varied between 4 and 11 per station in alpha-richness and between 5 and 17 per 200 m elevational interval in gamma-richness. The 95% confidence intervals for ACE overlapped between elevations in both data sets, hence not a single sampling site or elevational interval emerged statistically richest or poorest in the number of species. The two patterns responded to elevation in a very different way but any of the curves was decidedly humped. The mid-domain effect predictions failed to reproduce the pattern of observed or estimated species richness, and hence the ranges were located non-randomly along the elevational gradient. The pattern of distribution and diversity is supposedly generated by the environmental variables correlated to the elevation, which vary in a non-random manner with elevation.