The evolution of 2 spp belonging to the gen Tripterygion and some spp of the gen Blennius is discussed. Tripterygion tripteronotus and T. xanthosoma have very similar morphological characters yet live in 2 distinct niches. This probably results from 2 separate immigrations into the Mediterranean at different eras after the glacial age. After establishing reproductive barriers these populations would have evolved into 2 distinct spp. In contrast the spp of the gen Blennius were endemic in the Mediterranean and their evolution must have taken place after the end of the glacial age. During this lapse of time, multiple differentiations which might have taken place would account for the presence of sibling spp having comparable morphological characters but different ecological requirements. Blennius fluviatilis has a perimediterranean distribution in freshwater. It is possible that this sp originated from an ancestral sp which lived in the Mediterranean during the Miocene but took to the freshwaters during the Pliocene. B. pavo which is found in seawater and brackish waters of the East Atlantic and the Mediterranean probably originates from the same ancestral sp as B. fluviatilis. These examples illustrate the phylogenetic path of the Mediterranean fauna.