Author:

Keywords:

effective population size, fishery, genetic diversity, historical dna, microsatellites, solea solea, cod gadus-morhua, plaice pleuronectes-platessa, microsatellite null alleles, evolving fish stocks, marine fish, dover sole, overlapping generations, linkage disequilibrium, reproductive success, steelhead trout, Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Ecology, Evolutionary Biology, Environmental Sciences & Ecology, historical DNA, Solea solea, MICROSATELLITE NULL ALLELES, COD GADUS-MORHUA, MARINE FISH, DOVER SOLE, REACTION NORMS, DIVERSITY, ATLANTIC, CONSEQUENCES, FLOW, DNA, Animals, Fisheries, Flatfishes, Gene Frequency, Genetic Drift, Genetic Loci, Genetic Variation, Genetics, Population, Microsatellite Repeats, North Sea, Population Density, 06 Biological Sciences, 31 Biological sciences

Abstract:

Heavy fishing and other anthropogenic influences can have profound impact on a species' resilience to harvesting. Besides the decrease in the census and effective population size, strong declines in mature adults and recruiting individuals may lead to almost irreversible genetic changes in life-history traits. Here, we investigated the evolution of genetic diversity and effective population size in the heavily exploited sole (Solea solea), through the analysis of historical DNA from a collection of 1379 sole otoliths dating back from 1957. Despite documented shifts in life-history traits, neutral genetic diversity inferred from 11 microsatellite markers showed a remarkable stability over a period of 50 years of heavy fishing. Using simulations and corrections for fisheries induced demographic variation, both single-sample estimates and temporal estimates of effective population size (N-e) were always higher than 1000, suggesting that despite the severe census size decrease over a 50-year period of harvesting, genetic drift is probably not strong enough to significantly decrease the neutral diversity of this species in the North Sea. However, the inferred ratio of effective population size to the census size (N-e/N-c) appears very small (10(-5)), suggesting that overall only a low proportion of adults contribute to the next generation. The high N-e level together with the low N-e/N-c ratio is probably caused by a combination of an equalized reproductive output of younger cohorts, a decrease in generation time and a large variance in reproductive success typical for marine species. Because strong evolutionary changes in age and size at first maturation have been observed for sole, changes in adaptive genetic variation should be further monitored to detect the evolutionary consequences of human-induced selection.