Data from: Trophic level, successional age and trait matching determine specialization of deadwood-based interaction networks of saproxylic beetles

The specialization of ecological networks provides important insights into possible consequences of biodiversity loss for ecosystem functioning. However, mostly mutualistic and antagonistic interactions of living organisms have been studied, whereas detritivore networks and their successional changes are largely unexplored. We studied the interactions of saproxylic (deadwood-dependent) beetles with their dead host trees. In a large-scale experiment, 764 logs of 13 tree species were exposed to analyse network structure of three trophic groups of saproxylic beetles over 3 successional years. We found remarkably high specialization of deadwood-feeding xylophages and lower specialization of fungivorous and predatory species. During deadwood succession, community composition, network specialization and network robustness changed differently for the functional groups. To reveal potential drivers of network specialization, we linked species' functional traits to their network roles, and tested for trait matching between plant (i.e. chemical compounds) and beetle (i.e. body size) traits. We found that both plant and animal traits are major drivers of species specialization, and that trait matching can be more important in explaining interactions than neutral processes reflecting species abundance distributions. High network specialization in the early successional stage and decreasing network robustness during succession indicate vulnerability of detritivore networks to reduced tree species diversity and beetle extinctions, with unknown consequences for wood decomposition and nutrient cycling.

生态网络的特化程度为生物多样性丧失对生态系统功能的潜在影响提供了重要研究视角。然而，当前学界大多聚焦于生物间的互利与拮抗互作，而腐生生物网络及其演替动态尚未得到充分探索。我们针对枯木栖居甲虫（saproxylic beetles，依赖枯木生存的甲虫类群）与其枯木寄主间的物种互作展开研究。在一项大型野外实验中，我们布设了13个树种共计764根枯木样本，用以分析3个营养类群的枯木栖居甲虫在3年演替周期内的网络结构特征。研究结果显示，直接取食枯木的食木类甲虫（xylophages）具有极高的网络特化程度，而食真菌类与捕食性类群的特化程度相对较低。在枯木演替过程中，不同功能类群的群落组成、网络特化水平与网络鲁棒性呈现出差异化的变化趋势。为揭示网络特化的潜在驱动因素，我们将物种的功能性状（functional traits）与其在网络中的生态位角色进行关联，并检验了植物性状（如化学组分）与甲虫性状（如体型大小）间的匹配关系。研究发现，动植物双方的性状均为物种特化程度的关键驱动因子，且相较于反映物种多度分布（species abundance distributions）的中性过程（neutral processes），性状匹配（trait matching）对物种互作关系的解释力更强。演替早期阶段较高的网络特化程度，以及演替过程中网络鲁棒性的持续下降，表明腐生生物网络对于树木物种多样性降低与甲虫物种灭绝具有较高脆弱性，其对木质分解（wood decomposition）与养分循环（nutrient cycling）造成的潜在影响仍有待进一步明确。