Gentianella stiriaca , a case of reticulate evolution in the northeastern and eastern Central Alps

We gathered morphological and genetic evidence for introgressive patterns in Gentianella stiriaca , a taxon thought to have resulted from reticulate relationships between two or three species ( G. aspera, G. austriaca, G. rhaetica ). Multivariate analyses including morphometric and classical differential characters were poorly resolving and showed that G. stiriaca was mostly distributed within G. rhaetica and G. aspera . Using only the categorical classical differential characters, three well‐separated morphological groups ( G. aspera, G. austriaca, G. rhaetica ) were identified, however, with half of the G. stiriaca samples close to G. rhaetica . In contrast, AFLP data revealed several groups that were not concordant with morphological groups. Neighbour Joining, PCoA and Bayesian admixture analysis (BAPS) each identified a northeastern gene pool of G. aspera including northern samples of G. stiriaca , and a southeastern gene pool of G. rhaetica including southeastern G. stiriaca . Both gene pools show some admixture from G. austriaca . The genetic data support an old hypothesis of multiple hybrid origin and introgressive processes in the evolution of G. stiriaca . We discuss the effect of Pleistocene climate changes on the patterns of variation and introgression in Gentianella . We consider “ G. stiriaca ” a polytopic variant that does not deserve specific rank. Following the morphological species concept we propose including it in G. rhaetica to which it is most similar.