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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #221906
Title: Candidate loci reveal genetic differentiation between temporally divergent migratory runs of Chinook salmon (Oncorhynchus tshawytscha)

Author
item O'MALLEY, KATHLEEN - OREGON STATE UNIVERSITY
item Camara, Mark
item BANKS, MICHAEL - OREGON STATE UNIVERSITY

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2007
Publication Date: 12/1/2007
Citation: O'Malley, K., Camara, M.D., Banks, M.A. 2007. Candidate loci reveal genetic differentiation between temporally divergent migratory runs of Chinook salmon (Oncorhynchus tshawytscha). Molecular Ecology. 16: 4930-4941.

Interpretive Summary: An important question in managing and restoring endangered populations is whether or not they are genetically distinct from other populations of the same species. In Chinook salmon, this question is typically addressed using neutral genetic markers such as microsatellites. In California’s Feather, there are two seasonally distinct runs, the federally-listed threatened spring and more abundant fall run which are indistinguishable using these markers. In this paper, we show that two genes whose functions are a priori related to the timing of migration and spawning do, however, provide evidence for the genetic distinctiveness of these two runs and that these loci are likely to be under selection. These genes are Clock, an essential gene of the endogenous circadian clock and Ots515NWFSC, a microsatellite locus homologous to two salmonid genes central to the development of reproductive function. We argue that candidate genes can be more powerful at discriminating among populations than neutral loci and that these two genes in particular play a role in adapting these runs to their respective seasons.

Technical Abstract: Local adaptation is a dynamic process driven by selection that can vary both in space and time. One important temporal adaptation for migratory animals is the timing of migration and breeding within a reproductive season. Anadromous salmon are excellent subjects for studying the genetic basis of temporal adaptation because their high homing fidelity promotes reproductive isolation leading to the formation of local populations across diverse environments. Among Pacific salmon species, Chinook (Oncorhynchus tshawytscha) demonstrate the most intra-annual variability in migration timing with individuals belonging to one of four seasonal runs. In most river systems, neutral genetic markers are routinely employed to discriminate among these migratory runs. In California’s Feather River, however, we found no evidence for significant genetic differentiation between the federally-listed threatened spring and more abundant fall run at nine microsatellite loci (Fst=-0.0002). In contrast, using two candidate loci, Clock, an essential gene of the endogenous circadian clock and Ots515NWFSC, a microsatellite locus homologous to two salmonid genes central to the development of reproductive function, we found significant evidence for two genetically distinct migratory runs (OtsClock1b Fst=0.042, Ots515NWFSC Fst=0.058). Evidence presented here suggests that polymorphisms in OtsClock1b and Ots515NWFSC may influence migration and spawning timing of Chinook salmon in the Feather River.