Henter Heather J, Via Sara
Department of Entomology, Cornell University, Ithaca, New York, 14853.
Section of Ecology and Systematics, Cornell University, Ithaca, New York, 14853.
Evolution. 1995 Jun;49(3):427-438. doi: 10.1111/j.1558-5646.1995.tb02275.x.
For coevolution to occur, there must be genetic variation in each species for traits relevant to their interaction. Here, statistically significant variation in susceptibility to a parasitic wasp was found among pea-aphid clones collected from a single population. In a subset of clones that was tested further, wasps were found to oviposit in aphids from both resistant and susceptible lines, but eggs failed to develop in resistant hosts. Significant genetic variance in susceptibility provides evidence that this aphid population has the potential to evolve resistance in response to selection by one of its major natural enemies. Predictions of an expected response to selection based on the experimental measures of variation and field parasitism rates suggested that there should be a detectable change in susceptibility over the course of a season. However, an experimental comparison of mean susceptibility of clones collected early and late in the summer, a period of several generations, revealed no response to selection by the wasps. Aphids collected late in the season were as susceptible, on the average, as those collected early in the summer. Possible constraints on the response of the aphids to selection by this natural enemy are considered.
为了发生协同进化，每个物种中必须存在与其相互作用相关性状的遗传变异。在此，从单个种群收集的豌豆蚜克隆中发现了对寄生蜂易感性的统计学显著变异。在进一步测试的一部分克隆中，发现寄生蜂在抗性品系和敏感品系的蚜虫中都能产卵，但卵在抗性宿主中无法发育。易感性的显著遗传变异提供了证据，表明该蚜虫种群有可能因受到其主要天敌之一的选择而进化出抗性。基于变异的实验测量和田间寄生率对选择预期反应的预测表明，在一个季节的过程中，易感性应该会有可检测到的变化。然而，对夏季早期和晚期（几代的时间段）收集的克隆的平均易感性进行实验比较，结果显示对寄生蜂的选择没有反应。季节后期收集的蚜虫平均而言与夏季早期收集的蚜虫一样易感。本文考虑了蚜虫对这种天敌选择反应可能存在的限制因素。
