Genetic characterization of the razor clam Solen marginatus (Mollusca: Bivalvia: Solenidae) in Tunisian coasts based on isozyme markers

The genetic diversity of the razor clam Solen marginatus (Pennánt, 1777) originating from three separated sampling areas of the Tunisian coasts was investigated using isozyme markers. Departures from Hardy–Weinberg equilibrium expectations were evaluated by means of F-statistics and exact probability tests. The average multiloci FIS value was negative (mean FIS = −0.137) and statistically significant (P < 0.001). A minor but significant genetic differentiation was detected among samples (mean FST = 0.015, P < 0.01), but without significant isolation by distance among these samples. Using a hierarchical analysis of molecular variance approach, the genetic structure between samples within sampling areas was weak, but statistically significant, while it was absent among the sampling areas. The maximum likelihood estimates of the migration rates gave a value of 0.037, indicating low levels of connectivity among the localities. Testing for mutation-drift equilibrium showed a recent genetic bottleneck in two samples colonizing polluted sites.

► Genetic diversity in S. marginatus of Tunisian coasts was studied by isozyme markers.
► High level of genetic variability and significant heterozygote excess were observed.
► Weak but consistent genetic differentiation was detected between samples.
► Overall, it is very likely that the genetic differentiation is due to pollution.