Berenbaum M R, Zangerl A R
Department of Entomology, 320 Morrill Hall, University of Illinois, 505 S. Goodwin, Urbana, IL, 61801-3795, USA.
Evolution. 1992 Oct;46(5):1373-1384. doi: 10.1111/j.1558-5646.1992.tb01130.x.
Depressaria pastinacella, the parsnip webworm, feeds almost exclusively on the flowers and fruits of Pastinaca sativa, the wild parsnip. Resistance to webworms in wild parsnip populations is largely attributable to genetically based variation in furanocoumarin chemistry; by differentially reducing fruit set among chemical phenotypes, parsnip webworms may act as selective agents on wild parsnip populations. To determine whether wild parsnip chemistry can act as a selective agent on webworm populations, it is necessary to establish that resistance mechanisms in the webworm to furanocoumarins are genetically based. In this study, we estimated the amount of genetic variation in behavioral and physiological responses of webworms to parsnip furanocoumarins. Virtually no variation was found among webworm families for feeding preferences for diets varying as much as fourfold in furanocoumarin content. Nor was significant variation found for mean furanocoumarin intake over the assay period, except in one case, in which maternal effects may account for differences among families. In contrast, substantial familial variation existed for cytochrome P450-mediated metabolism of bergapten and xanthotoxin, two host furanocoumarins. The presence of additive genetic variation in metabolism, and the absence of such variation in discriminative feeding behavior, suggests that adaptation to changes in furanocoumarin chemistry, resulting either from changes in the distribution of chemical phenotypes in parsnip populations or from shifts to new chemically different host plants, is likely to be facilitated by physiological rather than behavioral means.
欧洲防风草织叶蛾（Depressaria pastinacella）几乎只以野生欧洲防风草（Pastinaca sativa）的花和果实为食。野生欧洲防风草种群对织叶蛾的抗性很大程度上归因于呋喃香豆素化学性质的基因变异；通过不同程度地减少化学表型之间的坐果率，欧洲防风草织叶蛾可能对野生欧洲防风草种群起到选择作用。为了确定野生欧洲防风草的化学性质是否能对织叶蛾种群起到选择作用，有必要确定织叶蛾对呋喃香豆素的抗性机制是基于基因的。在本研究中，我们估计了织叶蛾对欧洲防风草呋喃香豆素的行为和生理反应中的遗传变异量。在呋喃香豆素含量相差四倍的不同饮食的取食偏好方面，几乎没有发现织叶蛾家族之间存在变异。在整个测定期间，平均呋喃香豆素摄入量也没有发现显著变异，只有一个案例除外，其中母体效应可能解释了家族之间的差异。相比之下，对于两种寄主呋喃香豆素——佛手柑内酯和花椒毒素的细胞色素P450介导的代谢，存在显著的家族变异。代谢中存在加性遗传变异，而在辨别性取食行为中不存在这种变异，这表明无论是由于欧洲防风草种群中化学表型分布的变化，还是由于转向新的化学性质不同的寄主植物，对呋喃香豆素化学性质变化的适应可能是通过生理而非行为方式来促进的。
