von Burg Simone, Ferrari Julia, Müller Christine B, Vorburger Christoph
Institute of Zoology, University of Zürich, 8057 Zürich, Switzerland.
Proc Biol Sci. 2008 May 7;275(1638):1089-94. doi: 10.1098/rspb.2008.0018.
Parasitoids are an important mortality factor for insects. Susceptibility to parasitoids should thus be under strong negative selection. Nevertheless, ample genetic variation for susceptibility to parasitoids is commonly observed in natural populations, suggesting that trade-offs may constrain the evolution of reduced susceptibility. This can be studied by assessing genetic variation for susceptibility and its covariation with other components of fitness. In a set of 17 clones of the peach potato aphid, Myzus persicae, for which good estimates of heritable variation for life-history traits were available, we found significant clonal variation for susceptibility to two of their common parasitoids: Aphidius colemani and Diaeretiella rapae. One clone, the only one harbouring a facultative endosymbiotic bacterium, Regiella insecticola, was entirely resistant to both parasitoids. Susceptibilities to the two parasitoids exhibited a positive genetic correlation close to unity, implying a general mechanism of defence. However, the susceptibility to parasitoids was uncorrelated to the clones' fecundity or rate of increase, providing no evidence for costs of the ability to resist parasitoids.
寄生蜂是昆虫的一个重要死亡因素。因此，对寄生蜂的易感性应该受到强烈的负选择。然而，在自然种群中通常观察到对寄生蜂易感性存在丰富的遗传变异，这表明权衡可能会限制易感性降低的进化。这可以通过评估易感性的遗传变异及其与其他适合度成分的协变来研究。在一组17个桃蚜克隆中，对于其生活史性状的遗传变异已有很好的估计，我们发现对两种常见寄生蜂——菜蚜茧蜂和甘蓝蚜茧蜂的易感性存在显著的克隆变异。有一个克隆，是唯一携带兼性内共生菌昆虫雷氏菌的克隆，对这两种寄生蜂完全具有抗性。对这两种寄生蜂的易感性表现出接近1的正遗传相关性，这意味着存在一种普遍的防御机制。然而，对寄生蜂的易感性与克隆的繁殖力或增长率无关，没有证据表明抵抗寄生蜂的能力存在代价。
