Abstract
Biological invasions and range expansions act as natural experiments for understanding evolutionary processes at and beyond a species’ range margin. However, unlike manipulative experiments, invasions and range expansions are less genetically tractable and often involve genotypes of uncertain origin that are subject to complex evolutionary pressures. Here, we replay the earliest stages of the colonization of the widespread North American plant species Mimulus guttatus (synonym Erythranthe guttata) in the United Kingdom. We established a common garden in the invaded range using northern and southern native genotypes, allowed plants to freely mate and recruit, and quantified the genomic contribution made after five growing seasons using whole genome pooled sequencing (Pool-Seq). Despite having lower genome-wide variation, northern genotypes contributed disproportionately to the experimental population, which showed a two-fold excess of northern relative to southern ancestry, with 63%–70% northern contribution across chromosomes. The experimental population also showed extensive individual admixture, which we detected using diagnostic short sequences (k-mers) in the Pool-Seq data. Our results indicate that preadaptation of northern genotypes, despite reduced genome-wide variation, may have facilitated the successful range expansion of M. guttatus into the UK. This work also demonstrates how “invade and resequence” experiments can be used to dissect the genomic processes underlying expansion beyond a species’ native range.
Funding Information
  • Natural Environment Research Council (NE/N006739/1)
  • Fonds De La Recherche Scientifique - FNRS (310030 _212388/1)
  • Biotechnology and Biological Sciences Research Council (BBS/E/D/30002275)
  • Biotechnology and Biological Sciences Research Council (BBS/E/RL/230001A)

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