Data from: Manifold influences of phylogenetic structure on a plant-herbivore network

Ecologists are increasingly aware of the interplay between evolutionary history and ecological processes in shaping current species interaction patterns. The inclusion of phylogenetic relationships in studies of species interaction networks has shown that closely related species commonly interact with sets of similar species. Notably, the degree of phylogenetic conservatism in antagonistic ecological interactions is frequently stronger among species at lower trophic levels than among those at higher trophic levels. One hypothesis that accounts for this asymmetry is that competition among consumer species promotes resource partitioning and offsets the maintenance of dietary similarity by phylogenetic inertia. Here, we used a regional plant-herbivore network comprised of Asteraceae species and flower-head endophagous insects to evaluate how the strength of phylogenetic conservatism in species interactions differs between the two trophic levels. We also addressed whether the asymmetry in the strength of the phylogenetic signal between plants and animals depends on the overall degree of relatedness among the herbivores. We show that, beyond the previously reported compositional similarity, closely related species also share a greater proportion of counterpart phylogenetic history, both for resource and consumer species. Comparison of the patterns found in the entire network with those found in subnetworks composed of more phylogenetically restricted groups of herbivores provides evidence that resource partitioning occurs mostly at deeper phylogenetic levels, so that a positive phylogenetic signal in antagonist similarity is detectable even between closely related consumers in monophyletic subnetworks. The asymmetry in signal strength between trophic levels is most apparent in the way network modules reflect resource phylogeny, both for the entire network and for subnetworks. Taken together, these results suggest that evolutionary processes, such as phylogenetic conservatism and independent colonization history of the insect groups may be the main forces generating the phylogenetic structure observed in this particular plant–herbivore network system.生态学家愈发意识到，演化历史（evolutionary history）与生态过程之间的相互作用，是塑造当前物种互作模式的关键因素。将系统发育关系（phylogenetic relationships）纳入物种互作网络的研究已证实，亲缘关系较近的物种通常会与相似的物种类群产生互作。值得注意的是，拮抗生态互作（antagonistic ecological interactions）中的系统发育保守性（phylogenetic conservatism）程度，在较低营养级（trophic level）的物种中往往要强于较高营养级的物种。有一项假说解释了这种不对称性：消费者物种间的竞争会促进资源分化（resource partitioning），并抵消系统发育惯性（phylogenetic inertia）对饮食相似性的维持作用。本研究以由菊科（Asteraceae）物种和花头内生昆虫（flower-head endophagous insects）构成的区域性植物-植食动物互作网络为研究对象，旨在评估物种互作中的系统发育保守性强度在两个营养级之间存在何种差异。此外，本研究还探讨了动植物间系统发育信号（phylogenetic signal）强度的不对称性，是否取决于植食动物类群整体的亲缘关系远近程度。研究结果表明，除此前已报道的组成相似性外，无论是资源物种还是消费者物种，亲缘关系较近的类群均共享更高比例的对应系统发育历史。将整个网络的分析结果与由系统发育范围更受限的植食动物类群构成的子网络进行对比后发现，资源分化主要发生在较深的系统发育层级中，因此即使在单系群子网络（monophyletic subnetworks）内的亲缘关系较近的消费者类群之间，也能检测到拮抗相似性的正向系统发育信号。营养级间的信号强度不对称性，在网络模块（network modules）反映资源系统发育的模式上体现得最为明显，这一规律适用于整个网络以及各子网络。综合来看，这些结果表明，诸如系统发育保守性以及昆虫类群独立定殖历史（independent colonization history）这类演化过程，可能是塑造本研究中这一特定植物-植食动物网络系统的系统发育结构的主要驱动力。