Weis Arthur E, Gorman Wendy L
Section of Ecology and Evolutionary Biology, Department of Biological Sciences, Northern Illinois University, DeKalb, IL, 60115.
Evolution. 1990 Jul;44(4):820-831. doi: 10.1111/j.1558-5646.1990.tb03807.x.
The sensitivity of genotypic expression to the environment can be depicted as the reaction norm, which is defined as the array of phenotypes produced by a single genotype over a range of environments. We studied selection on reaction norms of the gall-inducing insect Eurosta solidaginis (Diptera; Tephritidae), which attacks tall goldenrod Solidago altissima (Compositae). Gall size was treated as a component of insect phenotype and attributes of the host plant as environmental influences on gall development. Genetic differences in the response of gall size to plant lag time (the number of days before a plant responds to the gall maker) were examined. Reaction norms for full-sib families of flies were quantified as linear functions; the elevation of the function denoted gall size produced by the family averaged across all plants, and the function's slope denoted family sensitivity to lag time. Expected fitness of each family was regressed over reaction norm elevation and slope to yield selection gradients on these reaction norm parameters. Directional selection on gall size averaged across environments is four times stronger than selection on sensitivity. Yet, genetic variation for sensitivity contributes more than twice as much to gall phenotypic variance as family mean gall size. Our results suggest that selection on environmental sensitivity will be weak for populations restricted to a narrow segment of an environmental gradient, but strong for broadly distributed species.
基因型表达对环境的敏感性可以用反应规范来描述，反应规范被定义为单一基因型在一系列环境中产生的表型阵列。我们研究了对致瘿昆虫金蝇（双翅目；实蝇科）反应规范的选择，这种昆虫以高杆一枝黄花（菊科）为食。瘿大小被视为昆虫表型的一个组成部分，寄主植物的属性被视为对瘿发育的环境影响。我们研究了瘿大小对植物滞后时间（植物对致瘿者做出反应前的天数）反应的遗传差异。果蝇全同胞家系的反应规范被量化为线性函数；函数的截距表示该家系在所有植物上平均产生的瘿大小，函数的斜率表示家系对滞后时间的敏感性。将每个家系的预期适合度对反应规范的截距和斜率进行回归，以得出这些反应规范参数上的选择梯度。跨环境平均的对瘿大小的定向选择比对敏感性的选择强四倍。然而，敏感性的遗传变异对瘿表型变异的贡献是家系平均瘿大小的两倍多。我们的结果表明，对于局限于环境梯度狭窄区段的种群，对环境敏感性的选择将较弱，但对于广泛分布的物种则较强。
