Parasites affect food web structure primarily through increased diversity and complexity

Comparative research on food web structure has revealed generalities in trophic organization, produced simple models, and allowed assessment of robustness to species loss. These studies have mostly focused on free-living species. Recent research has suggested that inclusion of parasites alters structure. We assess whether such changes in network structure result from unique roles and traits of parasites or from changes to diversity and complexity. We analyzed seven highly resolved food webs that include metazoan parasite data. Our analyses show that adding parasites usually increases link density and connectance (simple measures of complexity), particularly when including concomitant links (links from predators to parasites of their prey). However, we clarify prior claims that parasites “dominate” food web links. Although parasites can be involved in a majority of links, in most cases classic predation links outnumber classic parasitism links. Regarding network structure, observed chang...食物网结构的比较研究已揭示了营养组织的共性规律，构建了简化模型，并实现了群落对物种丧失的鲁棒性评估。此类研究大多聚焦于自由生活物种。近期研究表明，纳入寄生虫会改变食物网结构。本研究旨在探究网络结构的此类变化，究竟源自寄生虫独特的生态位与功能性状，还是源于物种多样性与网络复杂度的改变。我们分析了7组包含后生动物寄生虫（metazoan parasite）数据的高分辨率食物网。分析结果显示，纳入寄生虫通常会提升网络的连接密度与连接度（二者均为衡量复杂度的简易指标），尤其当纳入伴随链接（即捕食者指向其猎物所携带寄生虫的链接）时效果更为显著。不过，本研究澄清了此前关于寄生虫"主导"食物网链接的论断。尽管寄生虫可参与绝大多数网络链接，但在多数场景下，经典捕食链接的数量仍多于经典寄生链接。就网络结构而言，观测到的变化...