Niche evolution and diversification in Middle Eastern stream salamanders (Paradactylodon): vulnerability to future climate change

The relict genus Paradactylodon is narrowly distributed in temperate forests throughout the Middle East region, including P. mustersi in Afghanistan, P. persicus, and P. gorganensis in northwestern and northeastern Iran. Recent phylogenetic analyses suggest that the Iranian Paradactylodon populations may belong to a single species, P. persicus. In this study, we addressed how climatic niche conservatism and/or niche divergence may have affected the evolution of all Paradactylodon species using ecological niche models and multivariate niche analyses to identify niche overlap and assess equivalency and similarity tests. We also used an ensemble of ten algorithms to predict Paradactylodon species distributions for recent (1970-2000) and future (2081-2100) climate conditions. The results show that future climate change may cause the loss of 80 to 97% of these species' suitable habitat, especially at lower elevations. The niche divergence hypothesis was supported by the results of niche equivalency tests on P. persicus vs. P. gorganensis (and vice versa) with moderate overlap (D = 0.23, I = 0.41) and P. persicus vs. P. mustersi (and vice versa) with little overlap (D = 0.05, I = 0.06). Meanwhile, the niche similarity test for the niche conservatism hypothesis revealed significant results for P. persicus vs. P. gorganensis, P. mustersi vs. P. persicus, and P. persicus + P. gorganensis (as a single species) vs. P. mustersi. Due to these complex evolutionary ecological patterns and allopatric distributions, we recommend that P. gorganensis be considered a valid subspecies.