Amphibians are in the midst of a sixth mass extinction, and human activities play a major role in pushing species towards extinction. Landscape anthropisation has impacts that indirectly threaten species, in addition to the obvious destruction of natural habitats. For instance, land modification may bring human-commensal species in contact with sister-clades from which they were previously isolated. The species in these new contact zones are then able to hybridise to the point of reaching lineage fusion, through which the gene pool of the two species merges and one of the parental lineages becomes extirpated. Here, we documented the patterns of hybridisation between the spatially restricted D. suweonensis and the widespread D. japonicus. On the basis of the analysis of Cytochrome c oxidase subunit I mitochondrial DNA sequences (404 individuals from 35 sites) and six polymorphic microsatellites (381 individuals from 34 sites), we revealed a generalised, bi-directional, and geographically widespread hybridisation between the two species. Evidence of fertile back-crosses is provided by relatively high numbers of individuals in cyto-nuclear disequilibrium, as well as the presence of hybrid individuals further south than the species distribution limit, determined on the basis of call properties. Hybridisation is an additional threat to the endangered D. suweonensis.
Bibliographical noteThis research was funded by the National Research Foundation of Korea, grant number 2017R1A2B2003579 awarded to J.Y., and by Small Grants for Science and Conservation of The Biodiversity Foundation in 2014, 2015, and 2016 to A.B. The APC was funded by the National Research Foundation of Korea, grant number 2017R1A2B2003579 awarded to J.Y.
We are indebted to Lee Donggeun, Han Hyojeong, Oh Sunmin, Sin Euncheong, Kim Junyoung, and Yi Yoonjung for their help during field work; to Roh Gyeongah and Choi Noori for the development of the microsatellite primers; and to Kim Sanha, Ahn Jaeha, Kim Miyeon, and Han Hyojeong for their help for permits.
- Conservation biology
- Extinction threat
- North East Asia