Data from: Responses of interspecific associations in mixed-species bird flocks to selective logging

1. Non-trophic interactions (or, inter-species associations) play a prominent role in determining community structure and function. Mixed-species bird flocks are networks of non-trophic associations that confer foraging and anti-predator benefits to participant species. Yet, the responses of these interspecific associations to anthropogenic environmental change are poorly understood. 2. Selective logging is pervasive in the tropics, and can affect associations in mixed-species bird flocks by altering resource availability and/or predation risk, or through the altered abundances of species participating in mixed flocks. Across a gradient of logging intensity, we examined how the number and strength of associations in two different mixed-species flock types responded to logging intensity, while simultaneously controlling statistically for changes in the abundances of species in response to logging. 3. Across the logging gradient, we used network analyses to: (a) quantify the proportion of potentially realisable associations, and (b) measure the strengths of these realised associations. For both these analyses, we used null models to investigate whether changes in the network properties of mixed flocks were simply abundance-driven, or congruent with expectations of how flock properties might be modified by selective logging. 4. In understorey flocks, after controlling statistically for changing abundances of participant species, the proportion of realised associations decreased with increasing logging intensity, whereas mean association strength did not show any relation with logging intensity. In midstorey flocks, both the proportion and mean strength of realised associations increased with increasing logging intensity. 5. Synthesis and application: By statistically separating abundance and behaviour-mediated effects, we show that interspecific associations in mixed-species bird flocks respond to potential resource and/or predation changes from logging, but that their functional roles persist in logged forest. We show that logged forests can conserve not only community richness, but also function. Thus, these logged forests must be prevented from ongoing conversion into non-forest habitats such as agriculture and plantation.21-Dec-2017

1. 非营养级相互作用（Non-trophic interactions，亦称种间关联）在调控群落结构与功能中扮演核心角色。混合物种种鸟群（mixed-species bird flocks）是一类由非营养级关联构建的网络，可为参与其中的物种带来觅食与反捕食收益。但目前学界对这类种间关联如何响应人为环境变化的认知仍较为薄弱。2. 选择性采伐在热带区域分布广泛，其可通过改变资源可获取性、捕食风险，或改变参与混合鸟群的物种种群丰度，对混合物种种鸟群的种间关联造成影响。本研究沿采伐强度梯度开展实验，在统计控制物种种群丰度随采伐变化的前提下，探究了两类不同混合鸟群的种间关联数量与强度对采伐强度的响应规律。3. 基于采伐强度梯度，我们采用网络分析方法完成两项分析：(a) 量化可实现关联的占比；(b) 测定这些已实现关联的强度。针对这两项分析，我们均使用零模型（null models）来验证混合鸟群的网络属性变化，究竟仅由物种种群丰度变化驱动，还是与选择性采伐对鸟群属性的预期调控效应一致。4. 对于林下层鸟群，在统计控制参与物种的丰度变化后，已实现关联的占比随采伐强度升高而降低，但平均关联强度与采伐强度并无显著相关性。而在中层鸟群中，已实现关联的占比与平均关联强度均随采伐强度升高而上升。5. 综合与应用：通过统计分离丰度与行为介导的效应，我们证实混合物种种鸟群的种间关联会响应采伐引发的资源与/或捕食风险变化，但其功能作用在经采伐的森林中仍得以保留。研究表明，经采伐的森林不仅能够保护群落物种丰富度，还能维系其生态功能。因此，必须阻止这类采伐后森林被持续转化为农业用地、人工林等非森林生境。2017年12月21日