Elevational gradients of species richness, community structure, and niche occupation of tropical rove beetles (Coleoptera: Staphylinidae: Steninae) across mountain slopes in Northern Thailand

Abstract

AbstractWe evaluated patterns of species richness, heterogeneity, niche occupation, and community structuring/similarity of staphylinid beetles of the subfamily Steninae across a 2500-m elevational gradient of a tropical mountain area in Northern Thailand. Predaceous Steninae were collected from a variety of habitat types. Increasing Sørensen dissimilarity with increasing elevation was explained by both species turnover (especially across the lower elevational zones) and declining numbers of species (especially across elevations > 1400 m). Unlike the strong decline of the number of species with increasing elevation, species density (i.e., total number of species divided by the number of collection sites at the respective elevational zone) showed a much smoother decline suggesting that the negative gradient in the number of species was superimposed by a land-area effect inherent in mountain shape. In both the litter-inhabiting species and waterfall-associated species, the numbers of species showed a mid-elevational peak. Species frequency was positively correlated to both elevational (“Dianous” and Stenus) and habitat niche width (Stenus only). Stenus showed high interspecific variety of wide to narrow niche widths for both elevation and habitat. Numbers of Palearctic and Oriental species deviated from statistical expectation, suggesting that climate niche conservatism has played a role in their elevational distribution. The distributional patterns of “Dianous” beetles, with their strong hygrobiont preferences associated with rocks in running water and waterfalls, are potentially explained by source–sink dynamics along mountain streams.