Selection on breeding date and body size in colonizing coho salmon, Oncorhynchus kisutch

摘要: Selection during the colonization of new habitat is critical to process local adaptation, but has rarely been studied. We measured form, direction, and strength selection on body size date arrival breeding grounds over first three cohorts (2003-2005) a coho salmon (Oncorhynchus kisutch) population colonizing 33 km made accessible by modification Landsburg Diversion Dam, Cedar River, Washington, USA. Salmon were sampled as they bypassed dam, parentage was assigned based genotypes from 10 microsatellite loci, standardized gradients calculated using number returning adult offspring fitness metric. Larger fish in both sexes produced more offspring, magnitude effect increased subsequent years for males, suggesting that low densities attenuated traditional size-biased intrasexual competition. For sexes, directional favoured early breeders 2003, stabilizing observed 2004 2005. Adults arrived, presumably bred, stream-rearing juvenile larger at common than later parents, providing possible mechanism linking viability. Comparison studies employing similar methodology indicated strong, particularly with respect reproductive timing. Finally, female mean success exceeded needed replacement all so expanded generation, demonstrating can proficiently exploit vacant habitat.