Genetic relationships among one non-endemic and two endemic mediterranean triplefin blennies (pisces, blennioidei)

Three triplefin blennies occur sympatrically in the Mediterranean Sea; Trip terygion tripteronotus and T melanurus are endemic, whereas T delaisi is al so found in the Eastern Atlantic. Although very similar in morphology, ecol ogy and behaviour, some striking differences exist among reproductive strat egies. Several authors proposed hypotheses on the evolution of these specie s. In order to enhance insight into the genetic structure of this genus, an enzyme electrophoretic survey was performed. Samples of 40 to 45 specimens of each species were collected near Calvi (Corsica, France). Twenty-four e nzyme loci were analysed, of which 17 appeared polymorphic. T delaisi showe d a high level of average observed heterozygosity (H-o) of 0.140, as oppose d to very low levels of 0.009 and 0.021 in T tripteronotus and T melanurus, respectively. Nei's genetic distance was 0.21 between T delaisi and T trip teronotus, 0.35 between T delaisi and T melanurus and 0.45 between T tripte ronotus and T melanurus. We hypothesise that divergence of these species st arted before the Pleistocene and that the endemic species survived the Plei stocene glaciations in refugia within the Mediterranean. The possibility th at T. tripteronotus and T delaisi diverged through sympatric speciation is discussed.