A MULTISPECIES APPROACH TO THE ANALYSIS OF GENE FLOW IN MARINE SHORE FISHES

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Abstract
Ten species of marine shore fishes with a wide range of life-history strategies were collected from four areas in southern California, U.S.A., and Baja California, Mexico, and examined for patterns of genetic differentiation. Multilocus D and FST values (based on 32–42 presumptive gene loci in each species) were both negatively correlated with estimated dispersal capability. These results were robust to variations in the number and type of loci used in the analysis and are compatible with the hypothesis that levels of genetic differentiation in these shore fishes are determined primarily by gene flow and genetic drift. There is no a priori reason to expect the observed correlation to result from natural selection or historical factors. The findings thus suggest that populations of these shore fishes are in at least a quasi-equilibrium with respect to migration, mutation, and genetic drift. Present data were also used to compare estimates of mNe obtained by three different methods. Estimates based on FST values calculated by the methods of Nei and Chesser (FST(N)) and Weir and Cockerham (FST(W)) were highly correlated, but FST(N) ≤ FST(W) for every species, leading to generally higher mNe estimates for Nei and Chesser's method. Estimates of mNe based on the frequency of private alleles (Slatkin, 1985a) were not as strongly correlated with dispersal capability as were FST and D values. A low incidence of private alleles in many species may be responsible for this relatively weak correlation and may limit the general usefulness of Slatkin's method. In spite of their sensitivity to natural selection, FST and D may be better indicators of relative gene flow levels for high gene flow species.
Funding Information
  • Marine Life Research Group
  • Chancellor's Associates
  • U. C. San Diego