Mitchell-Olds T, Bergelson J
Division of Biological Sciences, University of Montana, Missoula 59812.
Genetics. 1990 Feb;124(2):416-21.
Measurement of natural selection on correlated characters provides valuable information on fitness surfaces, patterns of directional, stabilizing, or disruptive selection, mechanisms of fitness variation operating in nature, and possible spatial variation in selective pressures. We examined effects of seed weight, germination date, plant size, early growth, and late growth on individual fitness. Path analysis showed that most characters had direct or indirect effects on individual fitness, indicating directional selection. For most early life-cycle characters, indirect effects via later characters exceed the direct causal effect on fitness. Selection gradients were uniform across the experimental site. There was no evidence for stabilizing or disruptive selection. We discuss several definitions of stabilizing and disruptive selection. Although early events in the life of an individual have important causal effects on subsequent characters and fitness, there is no detectable genetic variance for most of these characters, so little or no genetic response to natural selection is expected.
对相关性状的自然选择进行测量，可为适应度曲面、定向选择、稳定选择或分裂选择模式、自然界中起作用的适应度变异机制以及选择压力可能存在的空间变异提供有价值的信息。我们研究了种子重量、发芽日期、植株大小、早期生长和晚期生长对个体适应度的影响。通径分析表明，大多数性状对个体适应度有直接或间接影响，表明存在定向选择。对于大多数早期生命周期性状，通过后期性状产生的间接影响超过了对适应度的直接因果效应。整个实验地点的选择梯度是一致的。没有证据表明存在稳定选择或分裂选择。我们讨论了稳定选择和分裂选择的几种定义。虽然个体生命早期的事件对后续性状和适应度有重要的因果影响，但这些性状中的大多数没有可检测到的遗传方差，因此预计对自然选择几乎没有或没有遗传响应。
