The effects of drift and selection on latitudinal genetic variation in Scandinavian common toads (Bufo bufo) following postglacial recolonisation

Clinal variation is paramount for understanding the factors shaping genetic diversity in space and time. During the last glacial maximum, northern Europe was covered by glacial ice that rendered the region uninhabitable for most taxa. Different evolutionary processes during and after the recolonisat...

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Bibliographic Details
Published in:Heredity 2021-04, Vol.126 (4), p.656-667
Main Authors: Thörn, Filip, Rödin-Mörch, Patrik, Cortazar-Chinarro, Maria, Richter-Boix, Alex, Laurila, Anssi, Höglund, Jacob
Format: Article
Language:English
Subjects:
Adaptation
Animals
Biological Evolution
Bufo bufo
Bufo bufo - genetics
Data analysis
Divergence
Evolution
Flora
Genes
Genetic diversity
Genetic Drift
Genetic Variation
Genetics, Population
Ice cover
Molecular structure
Outliers (statistics)
Phylogeny
Refugia
Refugium
Selection, Genetic
Toads
Variance analysis
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Summary:Clinal variation is paramount for understanding the factors shaping genetic diversity in space and time. During the last glacial maximum, northern Europe was covered by glacial ice that rendered the region uninhabitable for most taxa. Different evolutionary processes during and after the recolonisation of this area from different glacial refugia have affected the genetic landscape of the present day European flora and fauna. In this study, we focus on the common toad (Bufo bufo) in Sweden and present evidence suggesting that these processes have resulted in two separate lineages of common toad, which colonised Sweden from two directions. Using ddRAD sequencing data for demographic modelling, structure analyses, and analysis of molecular variance (AMOVA), we provide evidence of a contact zone located between Uppland and Västerbotten in central Sweden. Genetic diversity was significantly higher in southern Sweden compared to the north, in accordance with a pattern of decreased genetic diversity with increasing distance from glacial refugia. Candidate genes under putative selection are identified through outlier detection and gene-environment association methods. We provide evidence of divergent selection related to stress response and developmental processes in these candidate genes. The colonisation of Sweden by two separate lineages may have implications for how future conservation efforts should be directed by identifying management units and putative local adaptations.
ISSN:0018-067X
1365-2540
1365-2540
DOI:10.1038/s41437-020-00400-x