Os padrões de coocorrência de Micrablepharus atticolus e M. maximiliani (Squamata, Gymnophthalmidae) variam com a escala geográfica

Abstract

Species distribution may be affected by factors like phylogeny, environmental filters, and biotic interactions, among others. However, these factors will operate in different ways in distinct scales. To investigate occurrence patterns in different geographic scales we used two congeneric lizards species, Micrablepharus atticolus and M. maximiliani, the only two species in the genus. Micrablepharus maximiliani is abundantly distributed over the south-american dry-diagonal, from the Caatinga biome in Northeastern Brazil to the Argentinian Chaco, while M. atticolus is endemic to the Cerrado biome. Using niche modeling techniques we found that the distribution of these species in a regional scale is significantly affected by climatic variables. Using local community data, we showed that in a scale involving the overlap area of both species distributions, the co-occurrence between the two species is less than expected by chance. In a scale of hundreds of meters, we showed that microclimatic variables are determinant in their distribution along environmental gradients. Comparing body size variation between sympatric and allopatric populations we showed that, in sympatry, M. atticolus is smaller and M. maximiliani is larger. This character displacement is presumably a function of negative interactions between the species. The geographic scale have, therefore, great influence on the co-occurrence patterns between species, and conclusions drawn from a particular scale can hardly be extrapolated to other scales.