Data from: Using functional responses to quantify interaction effects among predators

1. Predator diversity alterations have been observed in most ecosystems as a result of the loss and/ or addition of species. This has implications for predator-prey dynamics as non-trophic interactions among predators, so called multiple predator effects (MPE), are known to influence predation success. In addition, there is often a density-dependant relationship between prey availability and prey consumption (functional response). While MPE investigations are common in the literature, functional responses have rarely been incorporated into this field of predation ecology. 2. Here, we outline an experimental procedure that incorporates functional responses into multiple predator effect studies. Using three fish species with different functional traits as model predators (bluegill Lepomis macrochirus, southern mouthbrooder Pseudocrenilabrus philander and banded tilapia Tilapia sparrmanii), we assess intra- and inter-specific predator interaction outcomes on predator-prey dynamics. This was done by contrasting observed functional responses of heterospecific and conspecific combinations of predators with expected responses based on those of individual predators. 3. Multi-predator combinations produced variable results. Bluegill were the only species in which observed conspecific multi-predator functional responses matched those of expected based on individual performance (prey risk neutral effects). In contrast, prey risk reduction was observed for both mouthbrooder and tilapia conspecific multi-predator trials. Heterospecific combinations revealed strong prey risk reduction effects for mouthbrooder-tilapia and bluegill-tilapia trials, while mouthbrooder- bluegill multi-predator functional responses combined additively. These results are discussed within the context of behavioural traits of the species and the development of a trait-based predictive framework. 4. Using a functional response approach allowed for the assessment of multiple predator effects across a range of prey densities. We propose that the incorporation of within-guild predator combinations into classic functional response investigations will enhance predictive capacity development in competition and predation ecology.1. 多数生态系统中均已观测到捕食者多样性的改变，其诱因为物种的丧失或引入。这一现象会对捕食者-猎物动态产生影响，因为捕食者间的非营养级相互作用——即所谓的多重捕食者效应（multiple predator effects, MPE）——已知会影响捕食成功率。此外，猎物可获得性与猎物消耗量之间通常存在密度依赖关系，即功能响应（functional response）。尽管针对MPE的研究在文献中较为常见，但功能响应极少被纳入捕食生态学这一研究领域。 2. 本研究提出一种将功能响应纳入多重捕食者效应研究的实验流程。本研究选取三种具有不同功能性状的鱼类作为模式捕食者：蓝鳃太阳鱼（Lepomis macrochirus）、南方口孵丽鱼（Pseudocrenilabrus philander）以及带纹罗非鱼（Tilapia sparrmanii），旨在评估捕食者种内与种间相互作用对捕食者-猎物动态的影响。具体实现方式为：将观测得到的异种、同种捕食者组合的功能响应，与基于单个捕食者的功能响应所预测的响应进行对比。 3. 多捕食者组合产生了多样化的实验结果。仅蓝鳃太阳鱼的同种多捕食者功能响应观测值，与基于单个捕食者表现所预测的结果相符（即猎物风险中性效应）。与之相反，口孵丽鱼和带纹罗非鱼的同种多捕食者实验均观测到猎物风险降低现象。异种捕食者组合实验中，口孵丽鱼-带纹罗非鱼以及蓝鳃太阳鱼-带纹罗非鱼的组合均表现出显著的猎物风险降低效应，而口孵丽鱼-蓝鳃太阳鱼的多捕食者功能响应则以加性方式组合。本研究将结合物种的行为性状以及基于性状的预测框架的构建，对上述结果展开讨论。 4. 采用功能响应方法，能够在一系列猎物密度下评估多重捕食者效应。本研究提出，将同功能群内的捕食者组合纳入经典功能响应研究，将有助于提升竞争与捕食生态学领域的预测能力。