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Population differentiation in Pacific salmon: local adaptation, genetic drift, or the environment?

Canadian Journal of Fisheries and Aquatic Sciences

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Abstract

Morphological, behavioral, and life-history differences between Pacific salmon (Oncorhynchus spp.) populations are commonly thought to reflect local adaptation, and it is likewise common to assume that salmon populations separated by small distances are locally adapted. Two alternatives to local adaptation exist: random genetic differentiation owing to genetic drift and founder events, and genetic homogeneity among populations, in which differences reflect differential trait expression in differing environments. Population genetics theory and simulations suggest that both alternatives are possible. With selectively neutral alleles, genetic drift can result in random differentiation despite many strays per generation. Even weak selection can prevent genetic drift in stable populations; however, founder effects can result in random differentiation despite selective pressures. Overlapping generations reduce the potential for random differentiation. Genetic homogeneity can occur despite differences in selective regimes when straying rates are high. In sum, localized differences in selection should not always result in local adaptation. Local adaptation is favored when population sizes are large and stable, selection is consistent over large areas, selective diffeentials are large, and straying rates are neither too high nor too low. Consideration of alternatives to local adaptation would improve both biological research and salmon conservation efforts.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Population differentiation in Pacific salmon: local adaptation, genetic drift, or the environment?
Series title:
Canadian Journal of Fisheries and Aquatic Sciences
Volume
52
Year Published:
1995
Language:
English
Contributing office(s):
Alaska Biological Science Center
Description:
pp. 2762-2777
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
2762
Last page:
2777
Number of Pages:
16