Data from: Phylogenetic composition of host plant communities drives plant-herbivore food web structure

1. Insects tend to feed on related hosts. The phylogenetic composition of host plant communities thus plays a prominent role in determining insect specialization, food web structure, and diversity. Previous studies showed a high preference of insect herbivores for congeneric and confamilial hosts suggesting that some levels of host plant relationships may play more prominent role that others. 2. We aim to quantify the effects of host phylogeny on the structure of quantitative plant-herbivore food webs. Further, we identify specific patterns in three insect guilds with different life histories and discuss the role of host plant phylogeny in maintaining their diversity. 3. We studied herbivore assemblages in three temperate forests in Japan and the Czech Republic. Sampling from a canopy crane, a cherry picker and felled trees allowed a complete census of plant-herbivore interactions within three 0.1 ha plots for leaf chewing larvae, miners, and gallers. We analyzed the effects of host phylogeny by comparing the observed food webs with randomized models of host selection. 4. Larval leaf chewers exhibited high generality at all three sites, whereas gallers and miners were almost exclusively monophagous. Leaf chewer generality dropped rapidly when older host lineages (5-80 myr) were collated into a single lineage but only decreased slightly when the most closely related congeneric hosts were collated. This shows that leaf chewer generality has been maintained by feeding on confamilial hosts while only a few herbivores were shared between more distant plant lineages and, surprisingly, between some congeneric hosts. In contrast, miner and galler generality was maintained mainly by the terminal nodes of the host phylogeny and dropped immediately after collating congeneric hosts into single lineages. 5. We show that not all levels of host plant phylogeny are equal in their effect on structuring plant-herbivore food webs. In the case of generalist guilds, it is the phylogeny of deeper plant lineages that drives the food web structure whereas the terminal relationships play minor roles. In contrast, the specialization and abundance of monophagous guilds is affected mainly by the terminal parts of the plant phylogeny and does not generally reflect deeper host phylogeny.

1. 昆虫通常取食近缘寄主。因此，寄主植物（host plant）群落的系统发育组成在决定昆虫特化程度、食物网（food web）结构与多样性方面发挥着关键作用。既往研究显示，植食性昆虫（herbivorous insect）对同属（congeneric）与同科（confamilial）寄主具有显著偏好，这表明不同层级的寄主植物亲缘关系可能发挥着差异化的重要作用。
2. 本研究旨在量化寄主系统发育对定量型植物-植食性昆虫食物网结构的影响。此外，我们还针对3种具有不同生活史的昆虫功能群（guild）识别了特定模式，并探讨了寄主植物系统发育在维持其多样性中的作用。
3. 我们对日本与捷克共和国的3处温带森林中的植食性昆虫群落进行了调查。通过林冠塔吊（canopy crane）、高空作业车（cherry picker）及伐倒木开展采样，我们得以对3块0.1公顷样地内的食叶幼虫（leaf chewing larvae）、潜叶昆虫（miners）与造瘿昆虫（gallers）的植物-植食者互作进行全面普查。我们通过将观测得到的食物网与随机化寄主选择模型进行对比，分析了寄主系统发育的影响。
4. 食叶幼虫在所有3处样地均表现出较高的取食广度（generality），而潜叶昆虫与造瘿昆虫则几乎完全为单食性（monophagous）。当将较古老的寄主谱系（500万至8000万年前）合并为单一谱系时，食叶幼虫的取食广度会迅速下降；但仅将亲缘关系最近的同属寄主合并时，其取食广度仅出现小幅降低。这表明，食叶幼虫的广食性是通过取食同科寄主维持的，而仅有少数植食者会共享亲缘关系更远的植物谱系，且令人意外的是，部分同属寄主之间也几乎不共享植食者。与之相反，潜叶昆虫与造瘿昆虫的取食广度主要通过寄主系统发育的末端分支维持，当将同属寄主合并为单一谱系后，其取食广度会立即下降。
5. 我们的研究表明，并非所有层级的寄主植物系统发育对植物-植食性昆虫食物网结构的影响都等同。对于广食性功能群而言，驱动食物网结构的是深层植物谱系的系统发育关系，而末端亲缘关系仅发挥次要作用。与之相反，单食性功能群的特化程度与多度主要受寄主植物系统发育的末端部分影响，通常无法反映深层寄主系统发育关系。