Role of colonization history and species-specific traits on contemporary genetic variation of two salamander species in a Holocene island-mainland system

Abstract

[Aim]: Investigate the role of colonization history and life history traits on contemporary patterns of genetic variation in two salamander species in a Holocene island‐mainland system.

[Location]: Rías Baixas, north‐western Spain.

[Methods]: We analysed mitochondrial and species‐specific nuclear markers (eight microsatellite markers) in 16 populations of Salamandra salamandra and Lissotriton boscai. Contemporary gene flow patterns between mainland and island populations were evaluated by migration analyses, whereas approximate Bayesian computation (ABC) was used to assess colonization history of insular populations of both species.

[Results]: Land bridge populations of both species exhibited reduced genetic diversity and increased genetic structure compared to mainland populations. ABC analysis showed that insular populations of both species were established by vicariance rather than by colonization via dispersal. We did not find evidence for contemporary gene flow, though the L. boscai insular population of Sálvora showed genetic admixture with mainland populations.

[Main conclusions]: This study supports the role of genetic drift in driving contemporary genetic variation of small and isolated populations. Other interplaying factors (e.g. island size, bathymetry) seemed to influence genetic variation, highlighting the importance of integrative studies to better understand the evolutionary dynamics of land bridge populations of amphibians.