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TRICOMM: Structure, assembly and evolution of natural tritrophic communities

TRICOMM：自然三营养群落的结构、组装和进化

基本信息

批准号：
NE/T000120/1
负责人：
Graham Stone
金额：
$ 73.38万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT000120%2F1
关键词：
TRICOMM Structure assembly evolution natural

项目摘要

Communities of plants, insect herbivores, and their insect parasitoid enemies provide most of the known species on Earth. These communities include interactions that lead to economic damage, such as pests of crops, and others that benefit human societies, such as biocontrol agents. Despite their importance, we still know little about what determines which species eat, or are eaten by, other species. We know most about links between plants and herbivores, less about herbivores and parasitoids, and less again about patterns over all three levels combined. A key question is the extent to which such three level (tritrophic) species associations are structured from the 'bottom-up' by plant traits, from the 'top-down' by parasitoids, or some combination of these. The 'bottom-up' view regards herbivore-parasitoid interactions as structured by processes happening a trophic level lower, via the effects of plants on herbivores. In contrast, the 'top-down' view sees parasitoid-herbivore interactions as driving the evolution of herbivore defences, and these traits as more important for structuring parasitoid communities than the host plants on which they are found.This project assesses the evidence for these alternative models, and their combinations, using state of the art statistical methods that require three types of data: (i) an interaction matrix, summarising links between species in one trophic level and those in another; (ii) herbivore defence trait data and (iii) complete species-level phylogenies for plants, herbivores and their parasitoids. Finding that plant phylogeny is a strong predictor of both plant-herbivore and herbivore-parasitoid interactions would support the bottom-up view. In contrast, finding that herbivore-parasitoid interactions are strongly predicted by herbivore defensive traits would support a top-down view. First, we will estimate the effects of species identity and traits on plant-herbivore and herbivore-parasitoid interactions, providing the first test of the relative importance of bottom-up versus top-down processes. We will use over 50,000 records of specific plant-herbivore-parasitoid interactions for natural communities comprising trees, gallwasp herbivores, and chalcid parasitoids, sampled from three regional datasets that span the Northern Hemisphere. These communities have evolved independently for long enough to provide largely independent tests of our hypotheses. Second, we ask whether herbivores in our three regional communities have independently evolved similar sets of defences. If top-down effects are strong, and herbivore defences target fundamental aspects of parasitoid attack behaviour, then selection should favour the repeated evolution of similar sets of defensive traits. Gallwasp herbivores live inside galls, complex novel plant tissues whose development the larval wasps induce. Parasitoids all attack gallwasps by drilling through gall tissues, and previous work suggests that some gall traits (such as coatings of spines or sticky resins) have evolved to make this more difficult. Our hypothesis is that such gall traits will both structure parasitoid communities and have evolved repeatedly.Finally, we will assess how well our statistical models predict which parasitoids attack a novel or unsampled gallwasp herbivore when all we know about it are which plant it is on, which gall traits it has, and how it is related to other gallwasps. Our approach involves making model-based predictions for gallwasp-parasitoid interactions for which we have real data, so that via cross-validation we can assess the accuracy (i.e. whether predictions are unbiased) and precision (i.e. whether predictions are made with high confidence) of our model. This approach could be of particular value in predicting the natural enemies of emerging pests and the non-target victims of natural enemies, and we will apply it to predicting the enemies attacking oriental chestnut gallwasp, a global pest species.

植物群落、食草昆虫和它们的昆虫寄生天敌提供了地球上大多数已知物种。这些群落包括导致经济损失的相互作用，如作物害虫，以及其他有益于人类社会的相互作用，如生物控制剂。尽管它们很重要，但我们仍然对是什么决定了哪些物种吃其他物种或被其他物种吃掉知之甚少。我们对植物和食草动物之间的联系了解得最多，对食草动物和寄生虫的了解较少，对所有三个层次的结合模式的了解也较少。一个关键的问题是，在何种程度上，这样的三个层次（三营养）的物种协会结构从“自下而上”的植物性状，从“自上而下”的寄生蜂，或这些的组合。“自下而上”的观点认为植食性寄生虫的相互作用是由发生在较低营养级的过程所构成的，通过植物对植食性寄生虫的影响。相反，“自上而下”的观点认为寄生虫-草食动物的相互作用推动了草食动物防御的进化，这些特征对于构建寄生虫群落比发现它们的宿主植物更重要。本项目使用最先进的统计方法评估这些替代模型及其组合的证据，需要三种类型的数据：（i）一个相互作用矩阵，总结了一个营养级的物种之间的联系，并在另一个;（ii）草食动物的防御性状数据和（iii）完整的植物，草食动物和他们的寄生虫物种水平的遗传。发现植物的寄生性是一个强有力的预测植物-草食动物和草食动物-寄生虫的相互作用将支持自下而上的观点。相比之下，发现草食动物的防御性状强烈预测草食动物寄生虫的相互作用将支持自上而下的观点。首先，我们将估计物种的身份和性状对植物-草食动物和草食动物-寄生虫相互作用的影响，提供自下而上与自上而下过程的相对重要性的第一个测试。我们将使用超过50，000个记录的特定植物-食草动物-寄生虫相互作用的自然群落，包括树木，gallwasp食草动物和小蜂寄生虫，采样从三个区域数据集，跨越北方半球。这些群落已经独立进化了足够长的时间，可以为我们的假设提供基本上独立的测试。第二，我们要问的是，在我们的三个区域社区中，食草动物是否独立地进化出了类似的防御机制。如果自上而下的影响是强大的，草食动物的防御目标的寄生攻击行为的基本方面，那么选择应该有利于重复进化的类似套防御性状。瘿蜂食草动物生活在瘿内，这是一种复杂的新植物组织，幼虫黄蜂诱导其发育。寄生蜂都是通过钻穿瘿组织来攻击瘿蜂的，以前的工作表明，一些瘿特征（如刺或粘性树脂的涂层）已经进化，使这变得更加困难。最后，我们将评估我们的统计模型预测哪些寄生蜂攻击一种新的或未采样的瘿蜂食草动物时，我们所知道的是它是在哪种植物上，它有哪些瘿特征，以及它是如何与其他瘿蜂相关。我们的方法涉及基于模型的预测，我们有真实的数据，因此，通过交叉验证，我们可以评估我们的模型的准确性（即预测是否无偏）和精度（即预测是否具有高置信度）。该方法在预测新出现害虫的天敌和天敌的非目标受害者方面具有重要价值，并将其应用于预测全球性害虫东方栗瘿蜂的天敌。