Gienapp P, Merilä J
Ecological Genetics Research Unit, Department of Biosciences, University of Helsinki, Helsinki, Finland; Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
J Evol Biol. 2014 Sep;27(9):1849-58. doi: 10.1111/jeb.12438. Epub 2014 Jun 14.
Spatial and temporal phenotypic differentiation in mean body size is of commonplace occurrence, but the underlying causes remain often unclear: both genetic differentiation in response to selection (or drift) and environmentally induced plasticity can create similar phenotypic patterns. Studying changes in body mass in Siberian jays (Perisoreus infaustus) over three decades, we discovered that mean body mass declined drastically (ca. 10%) over the first two decades, but increased markedly thereafter back to almost the initial level. Quantitative genetic analyses revealed that although body mass was heritable (h(2) = 0.46), the pronounced temporal decrease in body mass was mainly a product of phenotypic plasticity. However, a concomitant and statistically significant decrease in predicted breeding values suggests a genetic component to this change. The subsequent increase in mean body mass was indicated to be entirely due to plasticity. Selection on body mass was estimated to be too weak to fully account for the observed genetic decline in body mass, but bias in selection differential estimates due to environmental covariance between body mass and fitness is possible. Hence, the observed body mass changes appear to be driven mainly by phenotypic plasticity. Although we were not able to identify the ecological driver of the observed plastic changes, the results highlight the utility of quantitative genetic approaches in disentangling genetic and phenotypic changes in natural populations.
平均体型在空间和时间上的表型分化很常见，但潜在原因往往仍不清楚：对选择（或漂变）作出响应的遗传分化以及环境诱导的可塑性都能产生相似的表型模式。通过研究西伯利亚松鸦（Perisoreus infaustus）在三十年里体重的变化，我们发现平均体重在前二十年急剧下降（约10%），但此后显著增加，几乎回到了初始水平。数量遗传学分析表明，虽然体重具有遗传性（h(2) = 0.46），但体重随时间的显著下降主要是表型可塑性的结果。然而，预测育种值同时出现的且具有统计学意义的下降表明这种变化存在遗传成分。平均体重随后的增加表明完全是由可塑性导致的。据估计，对体重的选择力度太弱，无法完全解释观察到的体重遗传下降，但由于体重与适合度之间存在环境协方差，选择差异估计可能存在偏差。因此，观察到的体重变化似乎主要由表型可塑性驱动。虽然我们无法确定观察到的可塑性变化的生态驱动因素，但研究结果凸显了数量遗传学方法在解析自然种群遗传和表型变化方面的效用。
