Niche models at inter‑and intraspecifc levels reveal hierarchical niche diferentiationin midwife toads

Abstract

Variation and population structure play key roles in the speciation process, but adaptive intraspecifc genetic variation is commonly ignored when forecasting species niches.Amphibians serve as excellent models for testing how climate and local adaptations shape species distributions due to physiological and dispersal constraints and long generational times. In this study, we analysed the climatic factors driving the evolution of the genus Alytes at inter- and intraspecifc levels that may limit realized niches.We tested for both diferences among the fve recognized species and among intraspecifc clades for three of the species (Alytes obstetricans, A. cisternasii, and A. dickhilleni). We employed ecological niche models with an ordination approach to perform niche overlap analyses and test hypotheses of niche conservatism or divergence. Our results showed strong diferences in the environmental variables afecting species climatic requirements.At the interspecifc level, tests of equivalence and similarity revealed that sister species were non-identical in their environmental niches, although they neither were entirely dissimilar. This pattern was also consistent at the intraspecifc level, with the exception of A. cisternasii, whose clades appeared to have experienced a lower degree of niche divergence than clades of the other species. In conclusion, our results support that Alytes toads, examined at both the intra- and interspecifc levels, tend to occupy similar, if not identical, climatic environments.