The co-occurrence patterns of Micrablepharus atticolus and M. maximiliani (Squamata, Gymnophthalmidae) vary with geographic scale

Species distributions are affected by factors like phylogeny, environmental filters, and biotic interactions, among others. However, each factor operates in a different way at distinct scales. We used the only two congeneric species of Micrablepharus, M. atticolus and M. maximiliani, to investigate patterns of co-occurrence at different geographic scales. Micrablepharus maximiliani is abundantly distributed over the South American dry diagonal, from the Caatinga in northeastern Brazil to the Argentinian Chaco, while M. atticolus is endemic to the Cerrado. Using niche modeling techniques, we found significant overlap between the two species at the regional scale. However, they co-occur less than expected by chance where their areas of suitability overlap. At the local scale, their abundances are significantly associated with microclimate variation. Body size variation between sympatric and allopatric populations indicates that, in sympatry, M. atticolus is smallest and M. maximiliani is larger, revealing character displacement presumably resulting from species interactions. Co-occurrence patterns between the two species are strongly dependent on the spatial scale, and conclusions drawn from one scale should not be extrapolated to other scales.