Slow and steady wins the race: contrasted phylogeographic signatures in two Alpine amphibians

A deeper phylogeographic structure is expected for slow-dispersing habitat specialists compared to widespread adaptable species, especially in topographically complex regions. We tested this classic assumption by comparing the genomic (RAD-sequencing) phylogeographies of two amphibians inhabiting the Swiss Alps: the mobile, cosmopolitan common frog (Rana temporaria) against the stationary, mountain endemic Alpine salamander (Salamandra atra). Our results ran opposite of predictions: the frog displayed significantly higher genetic divergences and lower within-population variation compared to the salamander. This implies a prominent role for their distinctive glacial histories in shaping intraspecific diversity and structure: diversification and recolonization from several circum-Alpine micro-refugia for the frog versus a single refugium for the salamander, potentially combined with better population connectivity and stability. These striking differences emphasize the great variability of phylogeographic responses to the Quaternary glaciations, hence the complexity to predict general patterns of genetic diversity at the regional scale, and the forces that underlie them.

Automated summary

This study compared the genomic phylogeographies of two amphibians in the Swiss Alps, revealing that the common frog had higher genetic divergences and lower within-population variation compared to the Alpine salamander. The unique glacial histories of the frog and salamander played a significant role in shaping their intraspecific diversity and structure, emphasizing the variability of phylogeographic responses to the Quaternary glaciations.