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. 昆虫通常取食亲缘关系相近的寄主植物。因此，寄主植物群落的系统发育（phylogenetic）组成在决定昆虫特化程度、食物网结构与多样性方面发挥着关键作用。既往研究显示，植食性昆虫对同属（congeneric）及同科（confamilial）寄主具有显著的取食偏好，这表明不同层级的寄主植物亲缘关系对昆虫的影响程度存在差异。
2. 本研究旨在量化寄主植物系统发育对定量型植食性食物网结构的影响。此外，我们针对3种具有不同生活史的昆虫功能群（guild），分析其取食模式的特异性，并探讨寄主植物系统发育在维持昆虫多样性中的作用。
3. 我们在日本与捷克共和国的3处温带森林中开展了植食性昆虫群落调查。通过冠层起重机（canopy crane）、高空作业车（cherry picker）及伐倒木进行采样，我们对3块0.1公顷样地内的植食性昆虫与寄主植物的互作关系进行了全面普查，研究对象包括食叶幼虫、潜叶昆虫（miners）及造瘿昆虫（gallers）。我们通过将实测食物网与寄主选择的随机化模型（randomized models）进行对比，分析了寄主植物系统发育的影响效应。
4. 食叶幼虫在3处样地均表现出较高的取食广谱性（generality），而造瘿昆虫与潜叶昆虫则几乎完全为单食性（monophagous）。当将演化年代为500万至8000万年的古老寄主谱系（lineage）合并为单一谱系时，食叶昆虫的取食广谱性会快速下降；但仅将亲缘关系最近的同属寄主合并时，其取食广谱性仅出现小幅降低。这表明，食叶昆虫的广食性是通过取食同科寄主得以维持的，而在亲缘关系更远的植物谱系之间，以及部分同属寄主之间，共享的植食性昆虫种类极少——这一结果出人意料。与之相反，潜叶昆虫与造瘿昆虫的取食广谱性主要由寄主系统发育的末端分支（terminal nodes）维持，仅将同属寄主合并为单一谱系后，其取食广谱性便会立即下降。
5. 本研究表明，寄主植物系统发育的不同层级对植食性食物网结构的调控效应并不相同。对于广食性昆虫功能群而言，驱动食物网结构的是植物深层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，单食性昆虫功能群的特化程度与种群丰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谱系的系统发育关系。