Targets of selection
Although the phenotypes that we measured and observed in association with candidate SNPs cannot be concluded to be the causal variants that are the actual targets of selection, we can use the genotype-by-phenotype associations to guide future research aimed to identify these targets. Further, we can also narrow down some traits and life stages that do not appear relevant to any observed adaptive variation. For example, the adaptive genetic variation had no predictive ability for the short-term swimming ability of migration-phase adult lamprey at Bonneville Dam or the growth differences among young-of-year larvae. These two cases of failure to reject a null hypothesis help narrow down the search for a mechanism that manifests in large body size adults that tend to travel further upstream to spawn (a trait highly associated with genes on chromosome 2). These genes apparently do not confer adult swimming endurances, at least for the short timeframe that could be tested in swim trials at Bonneville Dam. Further, these adult body size differences do not translate to faster growth in young of year larvae. However, these adult body size differences could be influenced by differential growth at older life stages; prey selection, length of time in the ocean, or ocean distribution likely affect growth (Clemens et al. 2019). It will require further investigation of multiple life stages in both freshwater and the ocean to understand Pacific lamprey life history strategies. For the maturity trait, gene ontology could suggest other traits to examine as potential targets of selection including circadian rhythm.