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

ABSTRACT

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.

KEYWORDS:

• Dipsadidae
• Madeira-Purus interfluve
• Philodryas
• species distribution model
• RAPELD
• tropical rainforest

Acknowledgments

We acknowledge A.P. Lima, F. Werneck, E. Chilson and T. Gasnier that helped with useful considerations that improved this article. We are grateful to M. Ferrão, E. Farias, M.C. Araújo, P.I. Simões, M. Antunes, D. Bower, Pinduca, Neneco, Rubico, Joãozinho, Laudelino S. Vasconcelos and Philip Gleason for fieldwork assistance. Adrian Barnett helped with the English.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental Material

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Additional information

Funding

This fieldwork was supported by FAPEAM/CNPq - PRONEX under grant 653/2009. For logistical and institutional support we thank Programa de Pesquisa em Biodiversidade (PPBio), the National Institute for Science, Technology and Innovation for Amazonian Biodiversity (INCT-CENBAM), National Institute of Amazonian Research (INPA) and Programa de Grande Escala da Biosfera-Atmosfera na Amazônia (LBA). Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) provided a scholarship to T. A. C. Nogueira. I. L. Kaefer received a productivity grant from Brazilian National Council for Scientific and Technological Development (CNPq).