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

摘要

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