Cascading Generalism Shapes a Tritrophic Plant-Caterpillar-Parasitoid Network
Open Access Deposited(ii) quantify the level of parasitoid specialization within Limacodidae
(iii) compare my results to those of existing antagonistic networks
and (iv) evaluate the degree to which parasitoid use of limacodids is structured by plant identity. Quantitative network analysis of 951 plant-caterpillar-parasitoid interactions revealed a nested, uncompartmentalized, well-connected, and highly generalized system. Although the assemblage of common ⅴ parasitoids was broadly generalized within Limacodidae, there was some variation in host breadth, likely resulting from phenological differences and host size partitioning driven by interspecific competition. Interactions were weakly influenced by plant identity, a finding which is consistent with existing literature on limacodid polyphagy, and indicates a lack of reliance on species-specific plant cues for parasitoid host location. This connected, generalist architecture contrasts sharply with the modular, highly specialized, plant-driven patterns typical of antagonistic networks involving koinobiont parasitoids. Collectively, these findings challenge the paradigm of specialization among koinobiont parasitoids, provide a quantitative baseline for limacodid network structure in natural systems, and shed light on the nature of parasitoid interactions with polyphagous herbivores. Additionally, the lack of plant-driven structure in this system raises important questions as to how limacodid parasitoids locate, exploit, and specialize on their hosts, underscoring the need for further research into these mechanisms.
Due to the prevalence and ecological importance of insects, ecologists have longsought to characterize their interactions and the forces that structure their communities. Ecological network analysis provides a useful framework for quantifying these patterns. While most published network studies involve mutualisms, antagonistic interactions such as herbivory and parasitism are equally ubiquitous. Additionally, they are typically highly specialized, with consumers often having very narrow host ranges. A notable exception to this tendency is found in the moth family Limacodidae, whose larvae exhibit both extreme polyphagy and a variety of physical and chemical defenses against predators, making them excellent hosts for a diverse assemblage of parasitoids. Despite limacodids’ prevalence in eastern deciduous forests, the structure of this tritrophic system has never been formally quantified. To address this gap, I leveraged nearly two decades of rearing data from the greater Washington, D.C. area to construct the first tritrophic ecological network for North American Limacodidae, their host plants, and their parasitoids. By generating this network, I aimed to (i) analyze the overall structure of the network and determine whether these patterns deviate from null expectations
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