loading page

Inter-specific gene flow following the naturalization of a cultivated mint promotes the formation of a coalescent complex
  • +3
  • Jill Olofsson,
  • Torbjörn Tyler,
  • Luke Dunning,
  • Mats Hjertson,
  • Åke Rühling,
  • Anders Hansen
Jill Olofsson
University of Copenhagen

Corresponding Author:[email protected]

Author Profile
Torbjörn Tyler
Lund University
Author Profile
Luke Dunning
The University of Sheffield
Author Profile
Mats Hjertson
Uppsala Universitet
Author Profile
Åke Rühling
Lund University
Author Profile
Anders Hansen
University of Copenhagen
Author Profile

Abstract

Cultivation and naturalization of plants beyond their natural range can bring previously geographically isolated taxa together, thereby increasing the opportunity for hybridization and inter-specific gene flow, the outcomes of which are not predictable. These anthropogenic events therefore allow us to study how hybridization and inter-specific gene flow affect genetic and phenotypic diversity. Here, we explore the phenotypic and genomic effects of increased inter-specific gene flow following the re-introduction of the cultivated Mentha spicata (spearmint) into the ranges of the native mints M. longifolia and M. suaveolens. Using morphological analyses, we show that the cultivated M. spicata has altered trichome characters, which is likely a product of human imposed selection for a more palatable plant or a byproduct of selection on essential oil production. Using whole genome sequencing, we then show that there is extensive genetic admixture between the morphologically defined mint taxa that to some extent is mediated by the cultivated M. spicata. This has, at least partially, resulted in a breakdown of the species barriers. However, despite this breakdown, we find that genetic variants associated with the cultivated trichome morphology continue to segregate in cultivated, naturalized, and wild populations and we identify three genes that may function in the production of the characteristic aromatic oils of mints. Although hybridization can increase species richness by forming new hybrid taxa, we here show that unless reproductive barriers are strong it can also merge species into population/coalescent complexes over evolutionary time.