Niche incumbency, dispersal limitation and climate shape geographical distributions in a species-rich island adaptive radiation

Aim To test the role of climate, dispersal limitation and biotic interactions in limiting species' distributions within an island adaptive radiation by integrating species traits, phylogeny and estimates of dispersal cost into climate-based species distribution models. Location Hispaniola. Methods Focusing on 26 species of Anolis lizards, we used multivariate adaptive regression splines to evaluate the contribution of climate, species interactions, phylogenetic history and dispersal limitation to species distributional limits. For each species, we mapped the morphological similarity of congenerics using traits of known ecological import and predicted that species would be less likely to occur in climatically suitable areas if they were inhabited by ecologically similar species. Dispersal limitation was incorporated by generating spatially explicit estimates of dispersal cost, based on inferred habitat suitability. We compared models including morphological similarity, dispersal cost, phylogeny and climate with climate-only models. Results were evaluated against a null model that conserved the spatial structure of species occurrences. Results Climate had a dominant role in shaping species distributions. However, for over one-third of species we also found evidence consistent with supplemental effects of species interactions, i.e. ecological niche incumbency. These species were less likely to occur in climatically suitable areas inhabited by a morphologically similar species. Dispersal limitation also supplemented climatic limits in most species. These results were robust to co-variation with phylogeny and to comparison with our null model. Conclusions These results suggest that, rather than act as mutually exclusive alternatives, multiple dimensions of the ecological niche, including climatic limits, biotic interactions and dispersal capacity, interact to shape species distributions and that local interactions can influence the broad-scale geography of species in a predictable way.