Comparing evolvability and variability of quantitative traits.
Comparing evolvability and variability of quantitative traits.
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作者：
D. Houle
对数量性状的遗传变异进行比较有两个不同的原因。第一个是比较进化性，或对选择做出反应的能力，第二个是对维持遗传变异性的力量进行推断。用性状平均值标准化的变异度量，如加性遗传变异系数，对这两种目的都是合适的。变异通常被比作狭义的遗传力，但这几乎总是一个不恰当的进化性和变异性的比较措施。变异系数是根据文献中842个性状平均值、方差和遗传力的估计值计算的。与适合度密切相关的性状在弱选择条件下的加性遗传变异和非遗传变异均大于弱选择条件下的性状。这与基于遗传力比较的公认结论相反。适合度分量的低遗传力最好用它们的高残差变异来解释。适合度性状的高加性遗传和剩余变异性可能是由于它们受到大量遗传和环境事件的影响，或者由于缺乏稳定选择来减少它们的表型方差。超过三分之一的数量遗传学论文没有报告性状的平均值或方差。研究人员应始终报告这些统计数据，以便计算出适合各种情况的变异指标。
There are two distinct reasons for making comparisons of genetic variation for quantitative characters. The first is to compare evolvabilities, or ability to respond to selection, and the second is to make inferences about the forces that maintain genetic variability. Measures of variation that are standardized by the trait mean, such as the additive genetic coefficient of variation, are appropriate for both purposes. Variation has usually been compared as narrow sense heritabilities, but this is almost always an inappropriate comparative measure of evolvability and variability. Coefficients of variation were calculated from 842 estimates of trait means, variances and heritabilities in the literature. Traits closely related to fitness have higher additive genetic and nongenetic variability by the coefficient of variation criterion than characters under weak selection. This is the reverse of the accepted conclusion based on comparisons of heritability. The low heritability of fitness components is best explained by their high residual variation. The high additive genetic and residual variability of fitness traits might be explained by the great number of genetic and environmental events they are affected by, or by a lack of stabilizing selection to reduce their phenotypic variance. Over one-third of the quantitative genetics papers reviewed did not report trait means or variances. Researchers should always report these statistics, so that measures of variation appropriate to a variety of situations may be calculated.