Data from: Distribution of genetic variation underlying adult migration timing in steelhead of the Columbia River basin

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.