Genomic location of variation associated with adult migration timing within 1.3 Mb surrounding the GREB1L/ROCK1 region in Chinook salmon and steelhead. The x axes show genomic location and the y axes show the difference in allele frequency between early- and late-migrating fish. Top panel: difference in allele frequency between 64 spring-run and fall-run Chinook salmon from California (modified from Thompson et al. 2020). Bottom panel: allele frequency differences from pool-Seq between summer and winter steelhead from the Kalama and Klickitat Rivers, Columbia River, Washington (using data from Micheletti et al. 2018). Each point represents a variant, and color indicates the type of genome region each variant occurs in (genic, intergenic, etc.). Bottom track in each panel shows location of genes (triangles = direction of transcription, wide to narrow; vertical whiskers = exons) from each species’ genome annotation. GREB1L is colored orange, ROCK1 is colored violet. Note: although by some conventions names of genes appear in lower-case italics, here we use upper-case italics to be consistent with nomenclature in several recent salmonid publications for these genes.