Differentiated historical demography and ecological niche forming present distribution and genetic structure in coexisting two salamanders (Amphibia, Urodela, Hynobiidae) in a small island, Japan

Abstract

Background The climatic oscillations in the Quaternary period considerably shaped the distribution and population genetic structure of organisms. Studies on the historical dynamics of distribution and demography not only reflect the current geographic distribution but also allow us to understand the adaption and genetic differentiation of species. However, the process and factors affecting the present distribution and genetic structure of many taxa are still poorly understood, especially for endemic organisms to small islands. Methods Here, we integrated population genetic and ecological niche modelling approaches to investigate the historical distribution and demographic dynamics of two co-existing salamanders on Tsushima Island, Japan: the true H. tsuensis (Group A), and Hynobius sp. (Group B). We also examined the hypothesis on the equivalency and similarity of niches of these groups by identity and background tests for ecological niche space. Results Our result showed that Group A is considered to have undergone a recent population expansion after the Last Glacial Maximum while it is unlikely to have occurred in Group B. The highest suitability was predicted for Group A in southern Tsushima Island, whereas the northern part of Tsushima Island was the potential distribution of Group B. The results also suggested a restricted range of both salamanders during the Last Interglacial and Last Glacial Maximum, and recent expansion in Mid-Holocene. The genetic landscape-shape interpolation analysis and historical suitable area of ecological niche modelling were consistent, and suggested refugia used during glacial ages in southern part for Group A, and in northern part of Tsushima Island for Group B. Additionally, we found evidence of nonequivalence for the ecological niche of the two groups of the salamanders, although our test could not show either niche divergence or conservatism based on the background tests. The environmental predictors affecting the potential distribution of each group also showed distinctiveness, leading to differences in selecting suitable areas. Finally, the combination of population genetics and ecological modeling has revealed the differential demographic/historical response between coexisting two salamanders on a small island.

Demographic and ecological niche dynamics of the Vietnam warty newt, Paramesotriton deloustali: Historical climate influences

“…No signs of bottleneck events were found in the estimation of effective population size; however, the eSDM results indicate a reduction in the suitable range during the LGM in models for the overall population as well as the East and West groups (Fig 7). The contrasting results of demographic and species distribution modeling suggest a high population density of this species at the LGM [120]. Interestingly, suitable habitat areas tended to narrow down to high mountain ranges, such as the Hoang Lien Son Mountain Range (Fig 8G).…”

Ecological niche variation drives morphological differentiation in tropical stream‐dwelling newts from Indochina

“…The Species Distribution Modeling (SDM) approach utilizes environmental predictors to determine a potential species distribution based on known occurrence locations (Guisan & Thuiller, 2005). This approach is a powerful tool for predicting the distribution of several organisms, including salamanders and newts (e.g., Luo et al., 2022; Niwa et al., 2022; Tran et al., 2021; Vaissi, 2021). However, the optimal selection for modeling at a particular taxonomic level remains unclear because the prevalent practice of using species level as the primary unit often overlooks potential intraspecific variations (Smith et al., 2019).…”