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Research article - Peer-reviewed, 2021

Adaptive Introgression Facilitates Adaptation to High Latitudes in European Aspen (Populus tremula L.)

Rendon-Anaya, Martha; Wilson, Jonathan; Sveinsson, Saemundur; Fedorkov, Aleksey; Cottrell, Joan; Bailey, Mark E. S.; Runis, Dainis; Lexer, Christian; Jansson, Stefan; Robinson, Kathryn M.; Street, Nathaniel R.; Ingvarsson, Par K.


Understanding local adaptation has become a key research area given the ongoing climate challenge and the concomitant requirement to conserve genetic resources. Perennial plants, such as forest trees, are good models to study local adaptation given their wide geographic distribution, largely outcrossing mating systems, and demographic histories. We evaluated signatures of local adaptation in European aspen (Populus tremula) across Europe by means of whole-genome resequencing of a collection of 411 individual trees. We dissected admixture patterns between aspen lineages and observed a strong genomic mosaicism in Scandinavian trees, evidencing different colonization trajectories into the peninsula from Russia, Central and Western Europe. As a consequence of the secondary contacts between populations after the last glacial maximum, we detected an adaptive introgression event in a genome region of similar to 500 kb in chromosome 10, harboring a large-effect locus that has previously been shown to contribute to adaptation to the short growing seasons characteristic of Northern Scandinavia. Demographic simulations and ancestry inference suggest an Eastern origin-probably Russian-of the adaptive Nordic allele which nowadays is present in a homozygous state at the north of Scandinavia. The strength of introgression and positive selection signatures in this region is a unique feature in the genome. Furthermore, we detected signals of balancing selection, shared across regional populations, that highlight the importance of standing variation as a primary source of alleles that facilitate local adaptation. Our results, therefore, emphasize the importance of migration-selection balance underlying the genetic architecture of key adaptive quantitative traits.


adaptation; introgression; postglacial colonization; selective sweep; balancing selection

Published in

Molecular Biology and Evolution
2021, volume: 38, number: 11, pages: 5034-5050

Authors' information

Swedish University of Agricultural Sciences, Department of Plant Biology
Wilson, Jonathan
Swedish University of Agricultural Sciences, Department of Plant Biology
Sveinsson, Saemundur
Matís Ltd
Fedorkov, Aleksey
Russian Academy of Sciences
Cottrell, Joan
Forest Research
Bailey, Mark E. S.
University of Glasgow
Runis, Dainis
Latvian State Forest Research Institute Silava
Lexer, Christian
University of Vienna
Jansson, Stefan
Umea University
Robinson, Kathryn M.
Umea University
Street, Nathaniel R.
Umea University
Swedish University of Agricultural Sciences, Department of Plant Biology

UKÄ Subject classification

Evolutionary Biology

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