Kingsolver J G, Hoekstra H E, Hoekstra J M, Berrigan D, Vignieri S N, Hill C E, Hoang A, Gibert P, Beerli P
Department of Zoology, University of Washington, Seattle, Washington 98195, USA.
Am Nat. 2001 Mar;157(3):245-61. doi: 10.1086/319193.
How strong is phenotypic selection on quantitative traits in the wild? We reviewed the literature from 1984 through 1997 for studies that estimated the strength of linear and quadratic selection in terms of standardized selection gradients or differentials on natural variation in quantitative traits for field populations. We tabulated 63 published studies of 62 species that reported over 2,500 estimates of linear or quadratic selection. More than 80% of the estimates were for morphological traits; there is very little data for behavioral or physiological traits. Most published selection studies were unreplicated and had sample sizes below 135 individuals, resulting in low statistical power to detect selection of the magnitude typically reported for natural populations. The absolute values of linear selection gradients |beta| were exponentially distributed with an overall median of 0.16, suggesting that strong directional selection was uncommon. The values of |beta| for selection on morphological and on life-history/phenological traits were significantly different: on average, selection on morphology was stronger than selection on phenology/life history. Similarly, the values of |beta| for selection via aspects of survival, fecundity, and mating success were significantly different: on average, selection on mating success was stronger than on survival. Comparisons of estimated linear selection gradients and differentials suggest that indirect components of phenotypic selection were usually modest relative to direct components. The absolute values of quadratic selection gradients |gamma| were exponentially distributed with an overall median of only 0.10, suggesting that quadratic selection is typically quite weak. The distribution of gamma values was symmetric about 0, providing no evidence that stabilizing selection is stronger or more common than disruptive selection in nature.
在自然环境中，表型选择对数量性状的影响有多强？我们回顾了1984年至1997年的文献，查找那些通过标准化选择梯度或差异来估计线性和二次选择强度的研究，这些研究针对的是野外种群数量性状的自然变异。我们整理了63项已发表的针对62个物种的研究，这些研究报告了超过2500个线性或二次选择的估计值。超过80%的估计值针对形态性状；行为或生理性状的数据非常少。大多数已发表的选择研究没有重复，且样本量低于135个个体，导致检测自然种群中通常报道的选择强度的统计功效较低。线性选择梯度|β|的绝对值呈指数分布，总体中位数为0.16，这表明强烈的定向选择并不常见。对形态性状和生活史/物候性状的选择中|β|的值存在显著差异：平均而言，对形态的选择比对物候/生活史的选择更强。同样，通过生存、繁殖力和交配成功率方面的选择中|β|的值也存在显著差异：平均而言，对交配成功率的选择比对生存的选择更强。估计的线性选择梯度和差异的比较表明，表型选择的间接成分通常相对于直接成分较小。二次选择梯度|γ|的绝对值呈指数分布，总体中位数仅为0.10，这表明二次选择通常相当微弱。γ值的分布关于0对称，没有证据表明在自然界中稳定选择比破坏选择更强或更常见。
