Allozymic taxonomy within the genus Melanopsis (Gastropoda: Cerithiacea) in Israel: A case in which slight differences are congruent

Molecular differences between the species of Melanopsis distinguished by Heller were studied by means of cellulose acetate gel allozyme electrophoresis on 26 Melanopsis populations from Israel: 6 M. buccinoidea Olivier, 1801; 8 M. saulcyi Bourguignat, 1853; 1 M. meiostoma Heller & Sivan, 2001; and 11 M. costata Olivier, 1804, represented by two subspecies: M. costata costata Olivier, 1804, and M. costata jordanica Roth, 1839. Fourteen loci (9 polymorphic) were scorable: Aat, Alp, Est-1, Est-2, Gpi, Hbdh, Idh-1, Idh-2, Iddh, Mdh, Mdhp, Mpi, Pgdh, Pgm. Mean sample size was 28.983; mean number of alleles per locus: 1.45 (1.1-1.7); polymorphic loci per population: 36.5% (14.3-57.1); mean observed heterozygosity: 0.085 (0.041-0.121); mean expected heterozygosity: 0.112 (0.045-0.170). Nei genetic distance (0.000-0.232, mean 0.0761, no significant association with geographic distance) and Cavalli-Sforza and Edwards arc genetic distance (0.054-0.441, mean 0.240, significant association with geographic distance) were computed for pairs of populations. Interpopulation differences were analyzed phenetically (correspondence analysis, UPGMA), and phylogenetically (neighbor-joining and Fitch-Margoliash additive trees). Despite the slight differentiation of the taxa, the results confirmed the distinctness of M. costata costata, M. costata jordanica and M. saulcyi although the speciation processes may not yet be completed. The molecular variability of M. buccinoidea was wider than that of all the other studied taxa together, and overlapped the variation ranges of each. It may be ancestral species to the others, which may have speciated as peripheral isolates. The position of M. meiostoma as a distinct species was not confirmed.