Niche segregation of terrestrial alpine beetles (Coleoptera) in relation to environmental gradients and phenology

Abstract

At Finse, south Norway (60°36′N, 7°30′E), 247 pitfall traps were set in forty‐seven alpine habitats. More than 21,000 individuals were caught, including thirteen species of Carabidae, forty‐six Staphylinidae and twenty‐eight species from other families. The locations were selected to maximize variation in soil water contents between the habitats, but minimize variation in time of snowmelt and aspect. Soil water content of the sites was highly correlated with soil organic content, and showed little variation between dry and rainy periods. A reciprocal averaging (RA) ordination of the sites and coleoptera species gave results similar to a direct gradient analysis based on soil water content of the sample sites, clearly showing the importance of habitat humidity. Riverside and mire habitats had the most distinct species composition. Niche segregation among the species was studied based on guild, soil humidity preference, seasonal activity pattern and altitudinal range. Most species were well separated along one or more of these niche dimensions. No species from the wettest habitats were autumn active, otherwise all permutations of the described niche dimensions were used. Carabids and herbivores from various families were all spring active, while 38% of the staphylinids, mainly in the subfamily Omaliinae, were autumn active. In cases where species were not clearly separated, their behaviour, morphology, size, diet, etc. were considered.