Finding localities for an endangered salamander using ecological niche models: A local versus global approach

Background/Question/Methods

When designing a conservation plan for an endangered species, it is important to know all of the localities in which the species occurs. One method for predicting species occurrence in a new locality is to use ecological niche modeling. It is not clear, however, whether an ecological niche model will provide better predictions if it is constructed from all of the known localities in a species’ range, or if it is constructed only from localities in the vicinity of where predictions need to be made. We addressed this question for the proposed Solano County Habitat Conservation Plan, which will outline the areas necessary to conserve the county’s populations of the endangered California tiger salamander. We used the ecological niche modeling program MAXENT to create two niche models: one based on all 610 known localities across the range of the California tiger salamander and one based on the 19 known localities in Solano County. We then identified the areas in which these two models made the most divergent predictions and attempted to survey all of the potential salamander breeding ponds in those areas.  

Results/Conclusions

We surveyed 226 ponds in Solano County to determine the presence/absence of California tiger salamanders. Of these ponds, 52 were found to contain California tiger salamanders. A paired t-test between the predictive qualities of the two ecological niche models at each pond revealed that the model based solely on localities in Solano County performed significantly better than the model based on all known localities (p < 0.001). Potential reasons for the success of the local model include local adaptation of the Solano County population, increased sensitivity of the local model to factors limiting the salamanders’ range in this region, and spatial autocorrelation, in which new localities are more likely to be discovered closer to known localities.