Ecological niche models make predictions about where a species does or could possibly occur. Besides the obvious utility of knowing where a species occurs, ENMs can also be used for hypothesis testing. This can be used to answer questions about past and future distributions of species or to test biogeographic hypotheses. In their 2008 paper "Competitive interactions between felid species may limit the southern distribution of bobcats Lynx rufus" Sánchez-Cordero et al. take an interesting approach of using ENMs across multiple species to test a biogeographic hypothesis.
The primary focal species modeled was the bobcat, however, several other felid species known to co-occur with bobcats were also concomitantly modeled in Mexico. The bobcat ranges from southern Canada to southern Mexico, and exists in a myriad of ecosystem types. In southern Mexico, bobcat distribution has a cut off at the Isthmus of Tehuantepec. Interestingly, no abiotic environmental changes occur at this cutoff point that would prevent the vagile bobcat from entering or surviving in this area east of the isthmus. Further, potential distribution models (which did not account for biotic predictor variables) for the bobcat show suitable habitat occurring south and east of the Isthmus of Tehuantepec, providing additional evidence that abiotic factors are not preventing the bobcat from living in these areas. Amazingly, when the other members of the felid community of Mexico were modeled, four of them show what visually appears to be an inverse distribution compared to the bobcat (Figure 1). Notably, these same four felids also occur south and east of the Isthmus of Tehuantepec. This visual evidence (which was also further backed by statistics) strongly suggests a competitive interaction of some sort between the bobcat and the other felids.
While the ENMs in this study can't be used to elucidate the nature of the competitive interactions occurring between the studied felids, they do provide robust evidence of some interaction occurring. The results further suggest that biotic interactions become increasingly important at southern distribution limits. This study also demonstrates the importance of having expert knowledge of the ecology of the focal species as well as the geography in which they exist. The authors were able to extract much more information from their models because of their knowledge around the relevant environment. Further, this study shows that ENMs can be used to test hypotheses and generate new and directed hypotheses before even stepping foot into the field. Utilizing the methods in this study will, no doubt, make studies of the same kind much more efficient in their execution.
Paper reference:
Sánchez-Cordero V., Stockwell D., Sarkar S., Liu H., Stephens C.R., Giménez J. (2008). Competitive interactions between felid species may limit the southern distribution of bobcats Lynx rufus. Ecography. 31(6): 757 - 764.
Figure 1 (unedited from Sánchez-Cordero et al. 2008)
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