Conner J, Via S
Department of Entomology, Cornell University, Ithaca, NY 14853.
Heredity (Edinb). 1992 Jul;69 ( Pt 1):73-83. doi: 10.1038/hdy.1992.96.
To determine whether genetic constraints on adaptive evolution were operating in a laboratory population of a flour beetle, Tribolium castaneum, we first estimated the direct selection acting on each of several body size traits. Strong selection in males for an increase in pupal weight and a decrease in the ratio of adult to pupal weight occurred. In addition, a non-significant trend for a decrease in adult width was found. No significant selection on females was detected, although there were trends toward an increase in pupal weight and a decrease in adult width. These estimates were then combined with estimates of the genetic variances and covariances of the traits to predict the multivariate response to selection, that is, the evolutionary change in the traits across one generation. These projections showed only a small predicted change in male pupal weight in spite of the strong selection on pupal weight, and a relatively large predicted increase in width in spite of the possible negative direct selection on this trait. Both of these results were due in part to the positive genetic covariance between pupal weight and width, and they therefore suggest the possibility of genetic constraints on adaptive evolution of these traits.
为了确定适应性进化的遗传限制是否在赤拟谷盗（Tribolium castaneum）的实验室种群中起作用，我们首先估计了作用于几种体型性状的直接选择。在雄性中，对蛹重增加和成虫与蛹重之比降低有强烈的选择作用。此外，发现成虫宽度有不显著的下降趋势。虽然有蛹重增加和成虫宽度下降的趋势，但未检测到对雌性的显著选择。然后将这些估计值与性状的遗传方差和协方差估计值相结合，以预测对选择的多变量响应，即性状在一代中的进化变化。这些预测表明，尽管对蛹重有强烈选择，但雄性蛹重的预测变化很小，而尽管对该性状可能存在负向直接选择，但宽度的预测增加相对较大。这两个结果部分归因于蛹重和宽度之间的正遗传协方差，因此它们表明这些性状的适应性进化可能受到遗传限制。
