Functional Gene Diversity and Migration Timing in Reintroduced Chinook Salmon

Reintroduction efforts, aimed at restoring populations of salmonid fishes above dams, are occurring in many rivers in the United States’ Pacific Northwest. The long-term success of these reintroductions will depend on a population’s adaptive potential, mediated by genetic diversity underlying fitness-related traits. We evaluated variation at OtsClock1b and OmyFbxw11, two genes associated with the circadian clock mechanism and Ots515NWFSC, a gene associated with reproductive timing, in reintroduced Chinook salmon from the South Santiam and South Fork McKenzie rivers in Oregon We also examined associations between the circadian genes and migration time to the spawning grounds. Our findings indicate that levels of genetic diversity in reintroduced salmon were similar to those observed in other, extant populations, suggesting that diversity has been maintained through the supportive breeding (hatcheries) and reintroduction efforts. We also observed some genetic differentiation between years (temporal differentiation) and populations (spatial differentiation), but little evidence that selection was driving this variation. However, OmyFbxw11 genotype was a significant predictor of migration timing. Reintroduced salmon may therefore be capable of an evolutionary response to ecological shifts that alter the adaptive landscape between fitness and arrival timing to the spawning grounds.