Ophrys annae and Ophrys chestermanii: an impossible love between two orchid sister species

The biological concept of species is founded on the presence of barriers that limit the gene flow and species delimitation represents a vivid topic in orchids. Studies on the reproductive isolation in mediterranean orchids often examine the gene flow between co-occuring species providing a relevant understanding of how species boundaries are maintained. In Ophrys, the role of post-mating boundaries are always been tought to be weak and, despite the relevant morphological and ethological differences, low phylogenetic diversity has been recorded. In contrast, not many studies are focused on the relevance of each barriers in close related species in island condition. Using a morphological approach and experimental crosses to evaluate post-mating barriers, here, we clarify the taxonomic position of two sardinian endemic orchid sister-species, Ophrys annae and Ophrys chestermanii, currently ascribed in the bornmuelleri group. In Ophrys, due their iper specialized pollination syndrome, premat...