Altitudinal variation in the taxonomic composition of ground-dwelling beetle assemblages in NW Patagonia, Argentina: environmental correlates at regional and local scales

Abstract.  1. Altitudinal gradients offer a unique scenario to elucidate how the increase in harsh climatic conditions towards the top of the mountain interacts with other environmental factors at regional and local scale to influence the spatial variation in local species composition and biodiversity maintenance. We analysed the altitudinal variation in the taxonomic composition of epigaeic beetle assemblages across five mountains in north-western Patagonia (Argentina) to address whether substantial change in species composition was associated (i) at regional spatial scale, with changes in vegetation types, and the presence of dry and moist mountains, and (ii) at local spatial scale, with variation in temperature, plant cover and richness and several soil characteristics. 2. We collected beetles using 486 pitfall traps arranged in fifty-four 100-m2 grid plots of nine traps settled at about 100 m of altitude apart from each other, from the base to the summit of each mountain. We used multivariate analyses to identify beetle assemblages and to evaluate their association with environment. 3. We identified different beetle assemblages, associated more with vegetation types rather than with mountains; indicator species showed higher degree of fidelity and specificity to vegetation types rather than to mountains. Local variation in temperature, plant cover and richness, and soil characteristics influence the variation in species composition. 4. Our study suggests the existence of a regional beetle fauna that is shared across these mountains. Major regional changes in vegetation types and local variation in environment drive the variation in the species composition of beetle assemblages at these latitudes.