Genetic change for earlier migration timing in a pink salmon population

Abstract

To predict how climate change will influence populations, it is necessary to understand the mechanisms, particularly microevolution and phenotypic plasticity, that allow populations to persist in novel environmental conditions. Although evidence for climate-induced phenotypic change in populations is widespread, evidence documenting that these phenotypic changes are due to microevolution is exceedingly rare. In this study, we use 32 years of genetic data (17 complete generations) to determine whether there has been a genetic change towards earlier migration timing in a population of pink salmon that shows phenotypic change; average migration time occurs nearly two weeks earlier than it did 40 years ago. Experimental genetic data support the hypothesis that there has been directional selection for earlier migration timing, resulting in a substantial decrease in the late-migrating phenotype (from more than 30% to less than 10% of the total abundance). From 1983 to 2011, there was a significant decrease-over threefold-in the frequency of a genetic marker for late-migration timing, but there were minimal changes in allele frequencies at other neutral loci. These results demonstrate that there has been rapid microevolution for earlier migration timing in this population. Circadian rhythm genes, however, did not show any evidence for selective changes from 1993 to 2009.

Evolution of phenology in a salmonid population: a potential adaptive response to climate change

“…Genetic monitoring of this late-migrating marker locus (LMML) demonstrated that a selective event, first evident in brood year 1989, had reduced the abundance of the latemigrating subpopulation and that these demographic changes have persisted over the subsequent 13 generations. These results provided compelling evidence that the shifting phenology of Auke Creek pink salmon has a genetic basis (Kovach et al 2012). …”

“…The temporal characteristics of the LMMA in adults were described previously (Kovach et al 2012), and we briefly present those results here so that comparisons can be made between adults and fry. In each generation from 1985 to 1989, the LMMA frequency increased substantially after the midpoint of the migration (Fig.…”

“…Estimating the overall frequency of the LMMA and its statistical certainty is complicated by the variation of daily return numbers and unequal sample representation throughout the migratory periods. These issues were addressed with a parametric bootstrap algorithm (Kovach et al 2012) that resampled alleles at the LMML (1000 iterations) in running 5-day pools of genetic samples collected during each fry migration. The algorithm divided the migration distribution each year into n 5-day periods, beginning on the first date in which genetic samples were collected.…”

Evolution of Marine Organisms under Climate Change at Different Levels of Biological Organisation

“…Currently it remains unclear whether the few examples that demonstrate observable adaptive evolution of traits in response to climate change (e.g., body size [43], migration timing [44], thermal responses [45]) are dictated by various independent genes (within their respective genetic networks), or by fewer key regulatory genes within their genetic or metabolic networks. This is important to consider since any changes in the 'upstream' network genes could have extensive and numerous effects on traits [37], and yet the network itself may also provide some redundancy and buffering against perturbations, whereby changes to regulatory genes do not influence the genes they regulate [46].…”

Pacific Salmon and Steelhead: Life in a Changing Winter Ocean

“…For example, increases in sea surface temperatures due to greenhouse gas emissions are predicted to shrink the thermal habitats of salmon over vast regions of the North Pacifi c Ocean and adjacent seas (Welch et al 1998a, b;Azumaya et al 2007;Abdul-Aziz et al 2011;Kaeriyama et al 2012Kaeriyama et al , 2014. Nevertheless, salmon are capable of rapid microevolution that may allow them to adapt quickly (within one or two generations) to climate change (Kovach et al 2012). At present, total commercial catches of Pacifi c salmon around the Pacifi c Rim, dominated by pink salmon O. gorbuscha and chum salmon O. keta, are near the all-time high levels since record keeping began (NPAFC 2014).…”