Contact zones and their consequences: hybridization between two ecologically isolated wild Petunia species

Abstract

Plant hybridization is frequently observed in nature and considered an important driver of angiosperm diversity. Species are thought to arise through the accumulation of morphological and genetic differences that promote their evolutionary independence, even in the presence of hybridization. Natural hybrid zones yield an excellent system to study the outcomes of hybridization in terms of species diversity. Two recently diverged species, Petunia axillaris and P. exserta, show floral differentiation attributed to attraction of varying pollinators. Previous studies suggested natural hybridization between these species to explain morphological floral polymorphisms found among individuals of P. exserta. Here, we analyse genetic and morphological diversity in plants from the contact zone between these species and from isolated populations of each species to evaluate natural hybridization and its consequences. We found that the species' integrity is maintained despite interspecific hybridization and introgression that drove the origin of a new lineage in P. exserta in the contact zones.