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.