ALLOZYME EVIDENCE FOR CRYPTIC SPECIATION IN SYMPATRIC POPULATIONS OF NASSARIUS SPP (MOLLUSCA, GASTROPODA)

The Nassarius reticulatus complex (Mollusca: Gastropoda) is a common a nd morphologically variable organism of the Lusitanian marine province . The taxonomic status of the different morphs has been the subject of considerable debate for over a century. About 50 individuals of each N. nitidus and N. reticulatus morphs were collected in November 1994 f rom the same area (Ria de Vigo, north-west Iberian Peninsula). Prelimi nary screening by allozyme electrophoresis for 27 enzymes resolved 24 presumptive enzyme loci. There were no deviations from the Hardy-Weinb erg expected proportions at most polymporphic loci for any morph. Five and two enzyme loci were completely and partially diagnostic loci, re spectively, between the morphs. The genetic identity of morphs (I=0.65 8+/-0.095) was characteristic of congeneric species. The absence of el ectrophoretically recognizable hybrids in sympatric populations provid es clear evidence that the two morphs are reproductively isolated with in the study area. These genetic results corroborate other reported bi ochemical, morphological and behavioural differences between the morph s. Consequently, these data strongly suggest that the taxa N. nitidus and N. reticulatus must be considered as separate species.