Title: Distribution of genetic variation underlying adult
migration timing in steelhead of the Columbia River basin
Authors: Erin E. Collins1, John S.
Hargrove2, Thomas A. Delomas2, Shawn
R. Narum1
Affiliations: 1 Columbia River Inter-Tribal
Fish Commission
2 Pacific States Marine Fisheries Commission, Eagle
Fish Genetics Lab, 1800 Trout Road, Eagle, ID 83616
Contact information: Hagerman Genetics Lab
3059-F National Fish Hatchery Road
Hagerman, ID 83332
Keywords: Oncorhynchus , anadromous, greb1L ,
population genetics, landscape genetics
Abstract
Fish migrations are energetically costly, especially when moving between
fresh and saltwater, but are a viable strategy for Pacific salmon and
trout (Oncorhynchus spp. ) due to the advantageous
resources available at various life stages. Anadromous steelhead
(O. mykiss ) migrate vast distances and exhibit variation for
migration phenotypes that have a genetic basis at candidate genes known
as greb1L and rock1 .
We examined the distribution of
genetic variation at 13 candidate markers spanning greb1L ,
intergenic, and rock1 regions versus 246 neutral markers for 113
populations (n = 9,471) of steelhead from inland and coastal lineages in
the Columbia River. Patterns of population structure with neutral
markers reflected genetic similarity by geographic region as
demonstrated in previous studies, but candidate markers clustered
populations by predominate genetic variation associated with migration
timing. Mature alleles for late migration had the highest frequency
overall in steelhead populations throughout the Columbia River, with
only 9 of 113 populations that had a higher frequency of premature
alleles for early migration. While a single haplotype block was evident
for the coastal lineage, we identified multiple haplotype blocks for the
inland lineage. The inland lineage had one haplotype block that
corresponded to candidate markers within the greb1L gene and
immediately upstream in the intergenic region, and the second block only
contained candidate markers from the intergenic region. Haplotype
frequencies had similar patterns of geographic distribution as single
markers, but there were distinct differences in frequency between the
two haplotype blocks for the inland lineage. Redundancy analyses were
used to model environmental effects on allelic frequencies of candidate
markers and significant variables were migration distance, temperature,
isothermality, and annual precipitation.
This study improves our
understanding of the spatial distribution of genetic variation
underlying migration timing in steelhead as well as associated
environmental factors and has direct conservation and management
implications.