Abstract

REUS, María L et al. Trophic interactions among native and exotic herbivorous mammals in the Ischigualasto Provincial Park (San Juan, Argentina). Ecol. austral [online]. 2017, vol.27, n.3, pp.392-403. ISSN 1667-782X.

The communities of herbivores are more frequently composed of native and exotic species. Exotic species, with a recent history of co-occurrence among them and with native species, would exhibit less resource distribution strategies than native species, which co-evolved together establishing relationships between them and their environment. Aiming to assess trophic relationships in a community of herbivores that co-occur in Ischigualasto Provincial Park, we analyzed seasonal diet compositions, trophic niche breadth and diet overlap, and made associations based on condition (native or exotic) and body size (large or small). In the hyper-arid Monte region, where the study was conducted, shrub cover was the most representative cover throughout the year. The diets of native and exotic herbivores were based on this functional group of plants. Particularly native species made intensive and sustained use of shrubs during both the wet and dry seasons. Exotic species showed higher similarity in their diets and a constant trophic niche breadth all over the year (broader than that of native species). There was less similarity among the diets of native species, and their trophic niche was narrower, particularly in the dry season. Diet overlap between natives and exotics showed no variations between seasons, not even considering species of similar body size. Probably, no important overlaps are detected in food resource use because of the low densities of exotic species currently present in Ischigualasto Provincial Park. In any event, we recommend permanent monitoring that allows assessing potential competition between native and exotic species.

Keywords : Cow; Diets; Donkey; Guanaco; European hare; Mara; Monte Desert; Viscacha rat.