TY - JOUR

T1 - Morphological and genetic evidence suggest gene flow among native and naturalized mint species

AU - Olofsson, Jill K.

AU - Tyler, Torbjörn

AU - Dunning, Luke T.

AU - Hjertson, Mats

AU - Rühling, Åke

AU - Hansen, Anders J.

N1 - Publisher Copyright: © 2024 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.

PY - 2024

Y1 - 2024

N2 - Premise: Cultivation and naturalization of plants beyond their natural range can bring previously geographically isolated taxa together, increasing the opportunity for hybridization, the outcomes of which are not predictable. Here, we explored the phenotypic and genomic effects of interspecific gene flow following the widespread cultivation of Mentha spicata (spearmint), M. longifolia, and M. suaveolens. Methods: We morphologically evaluated 155 herbarium specimens of three Mentha species and sequenced the genomes of a subset of 93 specimens. We analyzed the whole genomes in a population and the phylogenetic framework and associated genomic classifications in conjunction with the morphological assessments. Results: The allopolyploid M. spicata, which likely evolved in cultivation, had altered trichome characters, that is possibly a product of human selection for a more palatable plant or a byproduct of selection for essential oils. There were signs of genetic admixture between mints, including allopolyploids, indicating that the reproductive barriers between Mentha species with differences in ploidy are likely incomplete. Still, despite gene flow between species, we found that genetic variants associated with the cultivated trichome morphology continue to segregate. Conclusions: Although hybridization, allopolyploidization, and human selection during cultivation can increase species richness (e.g., by forming hybrid taxa), we showed that unless reproductive barriers are strong, these processes can also result in mixing of genes between species and the potential loss of natural biodiversity.

AB - Premise: Cultivation and naturalization of plants beyond their natural range can bring previously geographically isolated taxa together, increasing the opportunity for hybridization, the outcomes of which are not predictable. Here, we explored the phenotypic and genomic effects of interspecific gene flow following the widespread cultivation of Mentha spicata (spearmint), M. longifolia, and M. suaveolens. Methods: We morphologically evaluated 155 herbarium specimens of three Mentha species and sequenced the genomes of a subset of 93 specimens. We analyzed the whole genomes in a population and the phylogenetic framework and associated genomic classifications in conjunction with the morphological assessments. Results: The allopolyploid M. spicata, which likely evolved in cultivation, had altered trichome characters, that is possibly a product of human selection for a more palatable plant or a byproduct of selection for essential oils. There were signs of genetic admixture between mints, including allopolyploids, indicating that the reproductive barriers between Mentha species with differences in ploidy are likely incomplete. Still, despite gene flow between species, we found that genetic variants associated with the cultivated trichome morphology continue to segregate. Conclusions: Although hybridization, allopolyploidization, and human selection during cultivation can increase species richness (e.g., by forming hybrid taxa), we showed that unless reproductive barriers are strong, these processes can also result in mixing of genes between species and the potential loss of natural biodiversity.

KW - admixture

KW - allopolyploid

KW - hybridization

KW - indumentum

KW - introgression

KW - Mentha

KW - trichome

U2 - 10.1002/ajb2.16280

DO - 10.1002/ajb2.16280

M3 - Journal article

C2 - 38334273

AN - SCOPUS:85184899795

VL - 111

JO - American Journal of Botany

JF - American Journal of Botany

SN - 0002-9122

IS - 2

M1 - e16280

ER -