Data from: Predicting invasive species impacts: a community module functional response approach reveals context dependencies

1. Predatory functional responses play integral roles in predator-prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. 2. Other inter-specific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator-prey interactions and thus the predictive capability of the comparative functional response approach. 3. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus quantifying the context dependencies of parasitism and a higher-order fish predator on these functional responses. 4. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher-order fish predator. 5. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp., and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher-order fish predator. 6. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies.

1. 捕食功能反应（predatory functional response）在捕食者-猎物动态中扮演着核心角色，对其开展评估有助于更深入地理解并预测入侵物种的捕食影响。2. 然而，其他种间相互作用——如寄生作用与高阶捕食——能够改变捕食者-猎物间的相互关系，进而削弱比较功能反应方法的预测性能。3. 本研究构建四物种种群模块（four-species community module），包含高阶捕食者、目标本土/入侵捕食者、目标捕食者的寄生虫以及本土猎物，以此比较本土凯尔特湖钩虾（Gammarus duebeni celticus）与入侵普通钩虾（Gammarus pulex）这两种端足目动物（amphipods）对3种无脊椎猎物——水虱（Asellus aquaticus）、蚋属物种（Simulium spp.）、罗氏蜉蝣（Baetis rhodani）——的捕食功能反应，从而量化寄生作用与高阶鱼类捕食者对这些功能反应的情境依赖性。4. 功能反应实验结果表明，入侵端足目动物对3种猎物中的2种具有更强的捕食影响（即更短的处理时间），这与野外观测到的影响模式一致。该种群模块同时揭示，寄生作用对其中一种猎物存在情境依赖性影响：在高阶鱼类捕食者存在的条件下，寄生作用可进一步降低入侵端足目动物的捕食影响，或增强本土端足目动物的捕食影响。5. 两种捕食者的猎物部分取食情况相似，且取食发生频率按水虱、蚋属物种、罗氏蜉蝣的顺序逐渐提升。该现象与猎物密度升高呈正相关，但不受寄生作用或高阶鱼类捕食者的情境因素影响。6. 本研究证实，纳入多种情境依赖性因素后，比较功能反应法可作为预测和评估入侵物种影响的有效工具，这为该方法的适用性提供了支持。