Spatial and trophic niche of an assemblage of native and non-native herbivores of arid Argentina

The coexistence of ecologically similar species is facilitated by differential use of resources along habitat, diet, and/or temporal niche axes. We used feces of non-native rabbit (Oryctolagus cuniculus), hare (Lepus europaeus), goat (Capra hircus), and the native plains viscacha (Lagostomus maximus) to compare the utilization of spatial and trophic resources in an arid ecosystem of Argentina. We expected herbivores to present differential responses in the use of at least one of the niche axes (habitat and/or trophic) associated with seasonal changes in resource availability and according to the origin of the species (native, non-native). We evaluated habitat use and selection through Chi-squared goodness-of-fit tests and Bonferroni confidence intervals, and factors shaping habitat selection (particular components of the habitat type) using generalized linear mixed-effects models. We analyzed the seasonal compositions of diets, breadth of trophic niches, and dietary overlaps. The assemblage of herbivores did not segregate markedly in spatial resource use, showing that hares and goats were more generalist than rabbits and plains viscacha in the utilization of different habitat types. Native and non-native herbivores overlapped markedly in the trophic niche dimension but segregated to some degree in the use of space during wet and dry seasons. The four herbivores shared a similar diet composition. Among dietary items, grasses contributed high percentages during the wet season. Under conditions of resource limitation (dry season), the native plains viscacha differed in feeding strategy from the non-native herbivores. These results deepen our understanding of likely underlying mechanisms that allow coexistence of native and non-native herbivores in an arid ecosystem.