Microevolution in Alaskan Pink Salmon in Response to Warming
Kovach, R.P., Gharrett, A.J. and Tallmon, D.A. 2012. Genetic change for earlier migration timing in a pink salmon population. Proceedings of the Royal Society B 279: 3870-3878.
Focusing on Auke Creek, a small lake-outlet stream near Juneau, Alaska (USA), where there have been complete daily counts of all adult pink salmon migrating into the creek since 1971, Kovach et al. set out to use "phenotypic data on migration timing, archived genetic samples and data from a marker locus, the allele frequencies of which were experimentally altered more than 30 years ago, to determine whether change in migration timing in a population of pink salmon has a genetic basis (i.e., microevolution)." In doing so the three researchers determined that both even- and odd-year adult pink salmon that spawn in the warming Alaskan stream are migrating into freshwater nearly two weeks earlier than they did 40 years ago. They also found that experimental 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)." They also report that "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 natural loci."
Commenting on their findings, Kovach et al. say that "these results demonstrate that there has been rapid microevolution for earlier migration timing in this population," which has allowed both the odd- and even-year groups of salmon "to remain resilient to environmental change," as has also been demonstrated by Kinnison and Hairston (2007). And they note in closing that "population abundance in 2011 was the second highest on record," further indicating that the salmon of Auke Creek are "persisting through rapid temperature warming."
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