Gratten J, Wilson A J, McRae A F, Beraldi D, Visscher P M, Pemberton J M, Slate J
Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
Science. 2008 Jan 18;319(5861):318-20. doi: 10.1126/science.1151182.
The evolutionary changes that occur over a small number of generations in natural populations often run counter to what is expected on the basis of the heritability of traits and the selective forces acting upon them. In Soay sheep, dark coat color is associated with large size, which is heritable and positively correlated with fitness, yet the frequency of dark sheep has decreased. This unexpected microevolutionary trend is explained by genetic linkage between the causal mutation underlying the color polymorphism and quantitative trait loci with antagonistic effects on size and fitness. As a consequence, homozygous dark sheep are large, but have reduced fitness relative to phenotypically indistinguishable dark heterozygotes and light sheep. This result demonstrates the importance of understanding the genetic basis of fitness variation when making predictions about the microevolutionary consequences of selection.
自然种群在少数几代中发生的进化变化，往往与基于性状遗传性和作用于这些性状的选择力所预期的情况背道而驰。在索艾羊中，深色皮毛与体型大有关，体型大具有遗传性且与适应性呈正相关，但深色羊的频率却下降了。这种意外的微进化趋势可以通过颜色多态性的因果突变与对体型和适应性具有拮抗作用的数量性状基因座之间的遗传连锁来解释。因此，纯合深色羊体型大，但相对于表型上无法区分的深色杂合子和浅色羊，其适应性较低。这一结果表明，在预测选择的微进化后果时，理解适应性变异的遗传基础非常重要。
