Department of Entomology, The Pennsylvania State University, University Park, Pennsylvania.
Department of Entomology, University of Wisconsin-Madison, Madison, Wisconsin.
J Anim Ecol. 2019 Nov;88(11):1789-1798. doi: 10.1111/1365-2656.13063. Epub 2019 Jul 28.
Adult and juvenile herbivores of the same species can use divergent feeding strategies, and thus may inhabit and consume different parts of the plant. Because the expression of chemical defences often differs between host plant tissues, this variation may result in disparate performance outcomes for adult and juvenile conspecifics that feed on distinct dietary substrates. The goal of this study was to evaluate how host range may differ between adults and juveniles in a generalist herbivore. We addressed the impacts of among- and within-plant defence variation using the wood-feeding Asian longhorned beetle (Anoplophora glabripennis) and three host plants having a range of putative resistance. Impacts of host plants on adult and offspring performance were assessed using a series of controlled bioassays. We evaluated adult-feeding and egg-laying behaviours in choice and no-choice experiments using the different hosts, and subsequent offspring establishment. We then evaluated host plant chemical composition related to nutrition and defence. Different plants had strong impacts on adult performance, but these patterns did not extend to effects on offspring. Females were capable of developing eggs when provided Acer rubrum, but not Populus deltoides or Populus tomentosa. Females that produced eggs by feeding on A. rubrum, however, deposited eggs into all three plant species. Larvae hatched and consumed tissues in all three hosts. The differences between adult and juvenile utilization of Populus spp. were reflected in markedly higher salicinoid phenolic concentrations in bark (>2% dw), while wood had trace quantities. Our results demonstrate that plant resistance mechanisms can differentially act upon adult and juvenile life stages of a polyphagous herbivore when there is differential expression of chemical defences among plant tissue types. Anoplophora glabripennis has been a globally successful invader due in part to its broad host range, and our results suggest a mechanism that permits the beetle to exploit marginally resistant plants. This study has implications for how host range differs between insect feeding stages, which is particularly important for invasive, polyphagous species encountering novel food sources.
成年和未成年同种食草动物可以使用不同的觅食策略，因此可能栖息和消耗植物的不同部位。由于化学防御的表达在宿主植物组织之间经常不同，这种变化可能导致以不同饮食基质为食的成年和未成年同种个体的表现结果不同。本研究的目的是评估一种广食性食草动物的成虫和幼虫在宿主范围上可能存在的差异。我们使用木质部食性的亚洲长角天牛（Anoplophora glabripennis）和三种具有不同潜在抗性的宿主植物来评估种内和种内防御变化的影响。使用一系列对照生物测定法评估了宿主植物对成虫和后代表现的影响。我们在不同的宿主植物上评估了成虫取食和产卵行为，包括在选择和非选择实验中的行为，以及随后的后代建立。然后，我们评估了与营养和防御相关的宿主植物化学成分。不同的植物对成虫的表现有强烈的影响，但这些模式并不延伸到对后代的影响。当提供红花槭（Acer rubrum）时，雌虫能够发育产卵，但当提供枫杨（Populus deltoides）或毛白杨（Populus tomentosa）时不能。然而，通过取食 A. rubrum 产卵的雌虫将卵产入所有三种植物中。幼虫在所有三种宿主中孵化并消耗组织。在白杨属植物中，成虫和幼虫的利用差异反映在树皮中较高的柳醇类酚类浓度（>2%干重），而木材中则痕量存在。我们的结果表明，当植物组织类型之间存在化学防御的差异表达时，宿主植物的抗性机制可以对多食性食草动物的成虫和幼虫阶段产生不同的作用。亚洲长角天牛之所以能在全球范围内成功入侵，部分原因是其广泛的宿主范围，而我们的结果表明了一种机制，使这种甲虫能够利用边缘抗性植物。本研究对于昆虫取食阶段的宿主范围差异具有启示意义，对于遇到新食物来源的入侵性、多食性物种尤其重要。
