Table of Contents
ISRN Zoology
Volume 2012 (2012), Article ID 528745, 6 pages
Research Article

Climate and Competition Shape Species' Borders: A Study of the Panamint (Crotalus stephensi) and Speckled (Crotalus mitchellii) Rattlesnakes

1Department of Geological Sciences, Indiana University, Bloomington, IN 47405, USA
2Department of Biology, Indiana University, Bloomington, IN 47405, USA
3Department of Biology, University of Texas at Arlington, Arlington, TX 76019, USA

Received 3 November 2011; Accepted 4 December 2011

Academic Editors: E. Font and D. Park

Copyright © 2012 A. Michelle Lawing et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We used ecological niche modelling to study the relative roles of climate and interspecific interactions in defining the parapatric contact between closely related species (Crotalus mitchellii and C. stephensi) and to predict refugia during the last glacial maximum. The modelled suitable habitat for C. stephensi correctly predicts the existing parapatric border between it and C. mitchellii, suggesting that C. stephensi's range at the border is limited by climatic factors. In contrast, the suitable habitat for C. mitchellii does not correctly predict the existing parapatric boundary; rather the suitable habitat of this species extends into the range of C. stephensi, suggesting the latter species, not climatic factors, limit the range of C. mitchellii. Modelled refugia of C. stephensi are much smaller than modern suitable habitat and are partially situated at the current parapatric border, whereas the refugia of C. mitchellii are similar to its current suitable habitat, though also shifted to the south. Ecological niche modelling appears to be a useful tool for studying the interplay between climate and competition in determining boundaries between parapatric species. It also appears to be useful for predicting past suitable habitats of species, because predicted refugia are congruent with independent estimates from molecular phylogeography.