Dr. Gustavo Silva-Arias ist PostDoc in der Section of population genetics am Center of Life and Food Sciences Weihenstephan der Technischen Universität München.  
Abstract:
It is widely recognized that hybridization between closely related plant species is an important process in plant evolution because of its consequences to species adaptation and diversification. In this study, we aimed to disentangle patterns of diversification and to estimate introgression between Petunia axillaris and P. exserta. These species differ in pollination syndrome, mating system, morphology, and inhabit contrasting environments. We evaluated the strength of gene exchange between these two Petunia species through ~6k SNPs obtained with the GBS technique to genotype 58 individuals distributed among seven allopatric and two contact zones and assess the population structure, admixture, and gene flow among these populations. Additionally, a set of alternative demographic scenarios was assessed to test the support of different isolation-migration scenarios as well as the time, grade, and direction of interspecific gene flow. The genetic structure analyses showed poor differentiation between P. axillaris populations, while P. exserta has strong population structure based on geographical locations. We identified two active hybrid zones and documented admixture related with a recent secondary contact that is better explained by differences in mating systems and post-zygotic barriers. Our results indicated that species borders are well maintained, despite likely ongoing gene exchange. Finally, we discuss that despite the strong floral morphological differentiation, unequivocal molecular evidence of admixture suggests that widely disclosed differentiation of pollination syndrome in Petunia species might be less specific than previously believed.