LAUSR

Aims Quantification of the degree to which ecological niches change over evolutionary time-scales is important for deepening our understanding of evolutionary and ecological processes. Phylogenetic niche conservatism (PNC) is when closely related species differ less ecologically than expected by chance, whereas Phylogenetic Niche Divergence (PND) is when closely related species differ more ecologically than expected by chance. We present a new null model to test for PNC and PND (the random translocation and rotation (RTR) significance test), which we combine with a novel metric for quantifying niche overlap. Location Europe, North America and Madagascar. Methods The RTR null model comprises many thousands of replicates generated by randomly translocating and rotating the set of occurrence records for two populations (e.g. sister species) while maintaining the spatial configuration between all occurrences within each replicate. For each replicate, we calculate niche overlap as the proportion of the combined niche breadth that is shared by the two species, averaged over n environmental dimensions. This approach enables us to test whether the observed niche overlap is more or less than expected by chance given the environmental conditions present in the study area. We test the performance of our approach in comparison to other methods using both simulated and real case scenarios, including crested newts in Europe, pocket gophers in North America, and lemurs in Madagascar. Results We find that our measure of niche overlap performs better than other metrics in an artificial simulation scenario, and we find evidence for both PNC and PND in our case studies for Europe, North America and Madagascar. Our results demonstrate that both the RTR significance test and the novel metric of niche overlap are consistent with evolutionary theory and are suitable methods to test for PNC and PND. Main conclusions We make available scripts to implement the RTR test and metric of niche overlap, and expect that the methods will prove useful for addressing a broad set of questions relating to ecological niche evolution and speciation, particularly for restricted-range species for which few known occurrence records are available.