Natural selection, gene flow, and population
structure in marine fishes
Grant Pogson, Ph.D.
University of California, Santa Cruz
Wednesday, February 21, 2001
3:00 p.m.—Pacific Forum
High levels of gene flow have been implicated in producing uniform
patterns of genetic variation among populations of many marine fish
species. However, molecular genetic studies on a growing number of marine
fishes have revealed (1) small, but highly significant, genetic
differentiation among natural populations, and (2) shallow phylogeographic
structuring of both mitochondrial (mtDNA) and nuclear (nDNA) gene trees.
Both observations are consistent with the hypothesis that the recent
population history of marine fishes, rather than extensive gene flow per
se, is responsible for their weak population structure.
I will present genetic data on populations of the Atlantic cod, Gadus
morhua, from the northwestern Atlantic region that strongly suggest
that recent population history is responsible for their minimal genetic
differentiation. Our results suggest that interpreting limited genetic
differences among populations of marine fishes (or other organisms) as
reflecting high levels of ongoing gene flow should be made with caution.
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