Scale-dependent estimates of niche overlap and environmental effects on two sister species of Neotropical snakes

Detecting ecological patterns is highly dependent on the spatial scale of the analysis. However, the importance of scale has been poorly explored when testing environmental influences and estimating niche overlap between animal species. In this study, we tested the hypotheses that: 1) environmental influences on species distribution at different geographic scales will be distinct, 2) niche overlap limits species local occurrence. We modeled ecological distributions of Philodryas argentea (n = 319) and P. georgeboulengeri (n = 61) in the Amazonian biome at different spatial scales: local, using regression analysis along 880 km transect with evenly distributed plots; and broad, modeling occurrence data with a Maximum Entropy algorithm. Variables that contributed to P. argentea occurrence were tree cover and elevation at local scale and annual temperature range for broad scale. For P. georgeboulengeri, the most important variables at local and broad scales were tree cover and elevation, respectively. Niche overlap was estimated at 23% and niches were not similar. We conclude: 1) detection of the most relevant variables for distribution of both species is dependent on spatial scale used; 2) although limited, co-occurrence of species at local scale seems to be allowed by the high niche dissimilarity observed in broad scale.