Biogeographic barriers and environmental gradients reveal distribution limits in Hynobius salamanders

This study investigates the biogeographic barriers and environmental gradients that influence the distribution and niche segregation of seven Hynobius salamander species in South Korea. Using Ecological Niche Models (ENMs) developed with the Maxent software and 48 environmental variables, we conducted four niche overlap tests for each species pair: niche identity tests and background similarity tests to assess niche differentiation, lineage-breaking tests to evaluate species boundaries in relation to environmental shifts, and ribbon tests to determine whether unsuitable habitats serve as distributional barriers. The results indicated that significant biogeographic barriers, including both physical features such as rivers and mountains and environmental gradients, influence the range segregation of these salamanders. The study also identified distinct ecological niches among the species, with environmental gradients and unsuitable habitats acting as key factors shaping their distributions. These findings highlight the crucial role of biogeographic barriers in the distribution and speciation of Hynobius salamanders, emphasizing the need to consider these factors in conservation strategies aimed at preserving their ecological diversity and evolutionary trajectories.