Spatial distribution and habitat selection in coexisting species of mountain ungulates

摘要

One of the main objectives of community ecology is to understand the conditions allowing species to coexist, which requires identifying how co-occurring species use and share space and resources. Species of the same trophic level, such as large herbivores, are of fundamental interest in that context because competition for resources is likely. Segregation in space or on some axes of the ecological niche are processes allowing coexistence, yet, both are seldom studied jointly. Based on annual spring censuses collected for 11 yr, we analysed the degree of overlap in spatial distribution among chamois Rupicapra rupicapra and moufl on Ovis gmelini musimon , 2 species of similar size that coexist on the same alpine pastures. We further investigated whether they diff ered in terms of habitat selection processes, and identifi ed which environmental factors led to species being aggregated or segregated. Th e areas of intensive use for 2 species were more spatially aggregated than expected by chance. Habitat selection was studied using multivariate methods based on the niche concept, considering the presence of 1 species as an environmental variable for the other. Despite a large overlap in niches (88%), segregation was signifi cant as chamois preferred meadows dominated by Sesleria and Carex sempervirens while moufl on selected meadows dominated by Carex ferruginea and avoided being close to areas aff ected by human activities. Importantly, habitat selection within each species was not aff ected by the presence of the other species. Coexistence between these 2 species and spatial overlap may be permitted because resource partitioning occurs at a fi ne temporal and/or spatial scale. We underscore that joint approaches of spatial and ecological processes are necessary to disclose the type of interaction (neutral, facilitation or competition) at play within a community.