Habitat selection by two sympatric rodent species in the Monte desert, Argentina. First data for Eligmodontia moreni and Octomys mimax

Habitat selection in deserts is mainly modulated by the availability of resources. The basic hypotheses regarding coexistence of species in arid environments offer two possibilities: 1) coexisting species partition available resources (each species acting as a specialist) and 2) generalists coexist with specialists because the former use habitats which are underused or not selected by the latter. This study presents the first data on macro- and microhabitat selection by Eligmodontia moreni (Cricetidae) and Octomys mimax (Octodontidae), two rodent species which coexist in the most arid part of the Monte desert of Argentina. In order to evaluate both hypotheses, animals were trapped during two seasons (humid and dry) in six macrohabitats of the arid Monte (creosote bush scrub, mesquite woodlands, columnar cactus slopes, barrens, chical and saltbush). A multivariate analysis of variance was used to evaluate differences in PCA components of microhabitat (floristic composition and vegetation structure) among capture and control points. The resulting models suggest E. moreni to be described as a fine-grained generalist species, which would be segregated from the specialist O. mimax in shared macrohabitats by resource partitioning, basically related to substrate type and vegetation cover. Our findings accord with theories of community assembly involving generalist and specialist species.