CONCLUSION
Here we show that the introduction of the cultivated spearmint into the
range of closely related taxa has increased inter-specific gene flow
between traditionally recognized mint taxa. This has caused the
breakdown of species barriers and created a cradle for the birth of a
coalescent complex. We thus show that when reproductive barriers are
low, the likely outcome of increased hybridization is genetic swamping
and merging of previously identified species causing a decrease in the
overall species richness. Hence, similarly to the cases of
naturalization of cultivated taxa, range shifts associated with climate
changes can promote the loss of biodiversity even when habitats are
protected and species are able to adapt to the new environment. Despite
the large-scale genomic overlap among the studied mints, we find that
genetic variants associated with a cultivated morphology continue to
segregate within and among populations, and hence classical taxonomic
units are mostly morphologically supported. The dissociation between
genomic and morphological merging will therefore likely continue to
complicate taxonomic assignments among mints.