Department of Biology, Wesleyan University, Middletown, CT, 06459, USA.
Oecologia. 2013 Nov;173(3):971-83. doi: 10.1007/s00442-013-2658-z. Epub 2013 Apr 26.
Herbivore-carnivore interactions are influenced by the plants on which herbivores feed. Accordingly, dietary generalist herbivores have been shown to experience differential risk of mortality from carnivores on different host-plant species. Here, we investigate whether caterpillar density and host-plant quality play a role in driving variation in generalist forest caterpillar mortality from insect parasitoids using a large-scale, multi-year observational study. A total of 4,500 polyphagous caterpillars were collected from eight host-tree species in Connecticut deciduous forests over 5 years, and frequencies of mortality from insect parasitoids (flies and wasps) were compared across the eight host-plant species for the entire generalist caterpillar assemblage (76 species). Separate comparisons were made using seven numerically dominant generalist species, allowing us to account for variation in caterpillar species-specific parasitism risk. We find significant variation in parasitism frequencies of generalist caterpillars across the eight host-plant species when accounting for variation in caterpillar density. We find no support for an influence of caterpillar density on parasitism and no clear evidence for an effect of host-plant quality on parasitism. Therefore, the results of this study discount the hypotheses that variation in caterpillar density and host-plant quality are responsible for variation in parasitism frequencies across host-plant species. Instead, our findings point to other plant-related characteristics, such as plant-derived parasitoid attractants, which may have robust, community-wide effects.
食草动物-食肉动物的相互作用受食草动物所食用的植物的影响。因此，研究表明，杂食性食草动物在不同的宿主植物物种上，食肉动物对其造成的死亡率风险存在差异。在这里，我们利用一项大规模的多年观测研究，调查毛毛虫密度和宿主植物质量是否在驱动食虫性森林毛毛虫被昆虫寄生蜂捕食的死亡率变化中发挥作用。在康涅狄格州落叶林中，从 8 种宿主树上收集了总共 4500 只多毛虫，在 8 种宿主植物中比较了整个广义毛毛虫群（76 种）中昆虫寄生蜂（苍蝇和黄蜂）的死亡率频率。对 7 种数量占优势的广义种进行了单独比较，这使我们能够解释毛毛虫物种特异性寄生风险的变化。我们发现，当考虑到毛毛虫密度的变化时，广义毛毛虫在 8 种宿主植物中的寄生频率存在显著差异。我们没有发现毛毛虫密度对寄生有影响的证据，也没有明确的证据表明宿主植物质量对寄生有影响。因此，这项研究的结果否定了毛毛虫密度和宿主植物质量变化是导致宿主植物物种间寄生频率变化的假设。相反，我们的研究结果指向其他与植物相关的特征，如植物源寄生蜂引诱剂，这些特征可能具有广泛的、稳健的群落效应。
