Estimation of habitat suitability and landscape connectivity for Liaoning and Jilin clawed salamanders (Hynobiidae: Onychodactylus) in the transboundary region between the People’s Republic of China and the Democratic People’s Republic of Korea

Human activities and climate change have caused damage to the natural world, leading to increased attention on habitat protection. However, most conservation efforts focus on flagship species, while many other species lack protection and are gradually becoming extinct due to the lack of conservation efforts and public attention. The Liaoning clawed salamander (Onychodactylus zhaoermii) and the Jilin clawed salamander (Onychodactylus zhangyapingi) are two amphibians endemic to Northeast Asia, but they have not received enough conservation attention, and little is known about their distribution. In this study, we collected field survey and literature data for both species to obtain data on occurrence, and constructed ecological niche models (ENMs) to understand their suitable habitat and potential distribution. The ENMs revealed that the suitable habitat of O. zhangyapingi was primarily located within the Yalu River basin, as well as western and eastern mountains of the Democratic People’s Republic of Korea (DPR Korea). On the other hand, the suitable habitat for O. zhaoermii was mainly distributed in the Xiuyan area of Liaoning in China, the Changbai Mountains, and north of the Tumen River basin. Although there is currently no direct evidence of the species’ presence in DPR Korea, the ENM results support their putative presence in the nation, as there are large patches of suitable habitat. In addition, the connectivity model showed the presence of transboundary corridors between patches of suitable habitat, with some nodes (here defined as continuous patches of habitat enabling connection between suitable habitats) located in multiple provinces or within different countries. In addition, the two nodes with the lowest resistance distance value were contiguous with the nodes along the corridors. In our evaluation of the transboundary corridors in the eastern and western parts of the study area, we found that the surfaces located downstream along the Tumen River showed a better quality for corridor. However, the gradual fragmentation and disappearance of the landscape may lead the two species to extinction. Therefore, we recommend establishing a transboundary amphibian protection network in the China-DPR Korea river basin and encouraging collaborations for amphibian surveys and applied conservation projects in the Tumen River basin.