Species boundaries in the Ophrys iricolor group in Tunisia: do local endemics always matter?

Abstract

The potential high pollinator specificity and the mosaic of highly differentiated potential habitats in the Mediterranean have probably fueled species diversification in the sexually deceptive genus Ophrys. Several endemic species have been described whose taxonomic status remains questionable. By using a combination of morphological, chemical, behavioural and genetic analyses, we have investigated the taxonomic status of O. vallesiana, a presumed endemic species of the O. iricolor/eleonorae group in Tunisia. We have found that O. eleonorae and O. vallesiana produce similar odour bouquets, are attractive to the same pollinators, have overlapping flower morphology and are genetically indistinct. Thus, all experimental evidence supports the conclusion that, in spite of the observed morphological differences in plant height and flower number, the local endemic O. vallesiana clusters together with the widespread and co-occurring O. eleonorae. Concomitantly, our results exclude a putative origin of O. vallesiana as a hybrid taxon between O. eleonorae and O. gazella, even if hybridization between these two species can occur locally. Our study demonstrates the need for accurate and multidisciplinary investigations for the proper taxonomic delimitation of local endemics and highlights the complexity of the evolutionary dynamics in Ophrys species complexes.