COMPARING STRENGTHS OF DIRECTIONAL SELECTION: HOW STRONG IS STRONG?
COMPARING STRENGTHS OF DIRECTIONAL SELECTION: HOW STRONG IS STRONG?
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比较方向选择的强度：多强算强？
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
D. Houle
中科院分区：
文献类型：
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作者：
J. Hereford;T. Hansen;D. Houle
Lande方程是进化数量遗传学的基本方程，它把定向选择的反应描述为加性遗传方差和性状值相对适合度的选择梯度的乘积。性状或群体之间的遗传方差和选择梯度的比较需要标准化，因为两者都是尺度依赖的。朗德方程可以用两种方式标准化。用选定性状的方差进行标准化，得到以标准差为单位的响应，作为遗传力和方差标准化选择梯度的乘积。这种标准化混淆了选择和变异，因为表型方差是遗传方差的函数。或者，我们可以用性状平均值标准化Lande方程，得到对选择的比例反应，作为加性遗传方差的平方系数和平均标准化选择梯度的乘积。均值标准化选择梯度对于总结选择强度特别有用，因为适应度的均值标准化梯度本身就是一个强选择的方便基准。我们回顾了已发表的估计方向选择在自然群体中使用平均标准化选择梯度。只有38项已发表的研究提供了计算平均标准化梯度的所有必要信息。多变量平均标准化梯度的绝对值中位数显示，选择平均是54%的选择适应度。修正了绝对值引入的向上偏差后，中值降低到31%，仍然是非常强的选择。如此大的估计显然不能代表所有性状的选择。高估选择强度的一些可能来源包括混淆环境和基因型对适应性的影响，使用适应性组件作为适应性的代理，以及在出版或选择性状进行研究时的偏见。
Abstract The fundamental equation in evolutionary quantitative genetics, the Lande equation, describes the response to directional selection as a product of the additive genetic variance and the selection gradient of trait value on relative fitness. Comparisons of both genetic variances and selection gradients across traits or populations require standardization, as both are scale dependent. The Lande equation can be standardized in two ways. Standardizing by the variance of the selected trait yields the response in units of standard deviation as the product of the heritability and the variance-standardized selection gradient. This standardization conflates selection and variation because the phenotypic variance is a function of the genetic variance. Alternatively, one can standardize the Lande equation using the trait mean, yielding the proportional response to selection as the product of the squared coefficient of additive genetic variance and the mean-standardized selection gradient. Mean-standardized selection gradients are particularly useful for summarizing the strength of selection because the mean-standardized gradient for fitness itself is one, a convenient benchmark for strong selection. We review published estimates of directional selection in natural populations using mean-standardized selection gradients. Only 38 published studies provided all the necessary information for calculation of mean-standardized gradients. The median absolute value of multivariate mean-standardized gradients shows that selection is on average 54% as strong as selection on fitness. Correcting for the upward bias introduced by taking absolute values lowers the median to 31%, still very strong selection. Such large estimates clearly cannot be representative of selection on all traits. Some possible sources of overestimation of the strength of selection include confounding environmental and genotypic effects on fitness, the use of fitness components as proxies for fitness, and biases in publication or choice of traits to study.
影响因子：
3.3
作者：
D. Houle
通讯作者：
D. Houle