Morphological and genetic characterization in putative hybrid zones of Petunia axillaris subsp. axillaris and subsp. parodii (Solanaceae)

Petunia axillaris subsp. axillaris and P. axillaris subsp. parodii (Solanaceae) are closely related taxa primarily distinguished by their geographical distribution and floral morphology. Both are found in the southern South American Pampas ecoregion, with the latter also occurring in the Chaco ecoregion; in the Pampas, taxa occupying adjacent areas and intermediary morphologies have been observed. Here, we explored morphological traits and genetic polymorphisms to test the occurrence of hybrid zones between these taxa along the Negro River (Uruguay) and southern Brazil. Morphological data showed variation among the groups, although they could have some overlap. Genetic data also support the differences between them and hybrid zones. These findings suggest that the divergence between P. axillaris subspecies occurred with occasional hybridization in their contact zones.