Scale effects on the pattern and predictors of small mammal diversity along a local elevational gradient in the Great Basin

AimEvaluation of the generality of the diversity-elevation relationship has highlighted effects of scale (spatial extent and grain size) on pattern perception. In contrast, the effects of scale on the attribution of drivers of diversity along elevational gradients remain largely unexplored. This is important because many causal factors have been proposed, and remotely sensed data about abiotic factors are available at increasingly fine grain sizes. Here, we evaluate the effects both of the resolution of the species diversity estimate on the pattern perceived, and of environmental predictor grain size on the potential contribution to each pattern. LocationRuby Mountains, Nevada, western North America. MethodsFor the small mammal fauna along one local elevational gradient, we compared patterns among estimates of richness derived from site-based occurrences rarefied by survey effort and those inferred from interpolation across species' elevational ranges. Using an information-theoretic approach, we evaluated the relative importance of spatial and environmental factors in structuring each richness distribution. Climate and habitat were assessed at coarse and fine grain sizes. Comparisons were based on model fit and relative variable importance. ResultsWe find general congruence in the diversity-elevation relationship, with peak diversity near the midpoint of the sampled gradient. Despite this commonality in pattern, we find the attribution of underlying drivers is substantially influenced by the type of richness estimate and by the grain size of the predictor variables. Main conclusionsOur results illustrate that the factors identified as predictors of diversity can be sensitive to grain size, and that this sensitivity is not equally apparent under different measures of richness obtained from the same survey data. We call for broader discussion of scale effects and resolution appropriateness for elevational diversity gradients. This is particularly important because mismatches in scale may result in misguided conservation or management initiatives.