O papel da escala nas estimativas de sobreposição de nicho e de efeitos ambientais sobre duas espécies irmãs de serpentes neotropicais

Abstract

Detecting ecological patterns is highly dependent on spatial scale. However, scale has been poorly explored when testing environmental influences and estimating niche overlap between species. In this study, we tested the hypotheses that 1) environmental filtering acting on species distribution differs between two different geographic scales, and 2) niche overlap limits species occurrence at local scale. As study model we used two sister-species of arboreal snakes mostly distributed in the Amazon. We modelled ecological distribution of Philodryas argentea and P. georgeboulengeri on different spatial scales: local, using stepwise regression analysis along an 880 km transect with evenly distributed sampling plots; and wide (Amazon basin), using Maximum Entropy algorithm. Variables that contributed to P. argentea occurrence were tree cover at local scale, and elevation for wide scale. For P. georgeboulengeri, the most important variable in local and wide scales were tree cover and elevation, respectively. Niche overlap was estimated at 23% and niches were not similar or equivalent. We conclude that 1) detection of the most relevant variables for distribution of both species is dependent on spatial scale approached; and 2) although limited, coocurrence of both species at local scale seems to be allowed by the high niche dissimilarity observed in macro-scale.