Abstract
We 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.
Highlights
Biodiversity studies across elevational gradients, with their long tradition in ecology and faunistics (McCoy 1990; Lomolino 2001), have evaluated characteristic patterns of diversity, community structure, and endemism and related them to climatic, spatial, historic, and/or biotic hypotheses (Körner 2007; McCain and Grytnes 2010; Grytnes and McCain 2013)
We present the results of a quantitative field study on staphylinid beetles of the subfamily Steninae across an elevational gradient of a tropical mountain area in northern Thailand
Among the “Dianous” species at ITH, the highest species frequencies were attained by D. srivichaii (45%), D. obliquenotatus (30%), and D. karen (27%) (Online Resource 3)
Summary
Biodiversity studies across elevational gradients, with their long tradition in ecology and faunistics (McCoy 1990; Lomolino 2001), have evaluated characteristic patterns of diversity, community structure, and endemism and related them to climatic, spatial, historic, and/or biotic hypotheses (Körner 2007; McCain and Grytnes 2010; Grytnes and McCain 2013). Whereas several studies have addressed single factors or combinations thereof (Yu et al 2013; Corcos et al 2018; Szewczyk and McCain 2019), few have used different niche metrics to evaluate the influence of both evolutionary and ecological determinants on local diversity patterns. Perhaps such an approach has rarely been attempted because it requires knowledge of the full taxonomy at the species level, which is often unknown for arthropods in tropical regions. The advantage of calculated niche dimensions, is that they integrate a number of single explanatory evolutionary and ecological factors that usually co-vary along elevational gradients and are difficult to disentangle (Szewczyk and McCain 2019)
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