Spatial and temporal variation of mountain dung beetle assemblages and their relationships with environmental factors (Aphodiinae: Geotrupinae: Scarabaeinae)

The analysis of a large census of dung beetles from the southern Alps (108 samples; 85,478 specimens belonging to 59 species) showed that 1) elevation and vegetation type (Mediterranean versus temperate) greatly influenced the assemblage composition, 2) spatial factors have a greater effect than monthly variability, and 3) exposure (north versus south) is a stronger determinant than vegetation structure (grassland-semi-open habitat-forest). Environmental heterogeneity results in different assemblages dominated by related species: Scarabaeinae dominate during spring and summer on south-facing nonwooded habitats; and Aphodiinae dominate from spring to autumn on north-facing slopes and in forests, but on south-facing slopes only in autumn. Scarabaeinae species have similar spatiotemporal distributions; thus, it can be assumed that this subfamily is restricted in space and time by thermal sensitivity. The colonization of high elevations by small tunnelers is due to a few species that have a broad tolerance of environmental conditions. In contrast, the temporal distribution of Aphodiinae is highly segregated, and these beetles occupy a variety of habitats because of their specialization. Analysis shows the distribution of species belonging to different subfamilies is most related to biological requirements rather than interspecific competition.