Predicting the effects of climate change requires understanding complex interactions among multiple abiotic and biotic factors. By influencing key interactions among host species, parasites can affect community and ecosystem structuring. Yet, our understanding of how multiple parasites and abiotic factors interact to alter ecosystem structure remains limited. To empirically test the role of temperature variation and parasites in shaping communities, we used a multigenerational mesocosm experiment composed of four sympatric freshwater crustacean species (isopods and amphipods) that share up to four parasite species. Mesocosms were assigned to one of four different treatments with contrasting seasonal temperatures (normal and elevated) and parasite exposure levels (continuous and arrested (presence or absence of parasite larvae in mesocosm)). We found that parasite exposure and water temperature had interactive effects on the host community. Continuous exposure to parasites altered the community structure and differences in water temperature altered species abundance. The abundance of the amphipod Paracalliope fluviatilis decreased substantially when experiencing continuous parasite exposure and elevated water temperatures. Elevated temperatures also led to parasite-induced mortality in another amphipod host, Paracorophium excavatum. Contrastingly, isopod hosts were affected much less, suggesting increasing temperatures in conjunction with higher parasite exposure might increase their relative abundance in the community. Changes in invertebrate host populations have implications for other species such as fish and birds that consume crustaceans as well as having impacts on ecosystem processes, such as aquatic primary production and nutrient cycling. In light of climate change predictions, parasite exposure and rise in average temperatures may have substantial impacts on communities and ecosystems, altering ecosystem structure and dynamics.

中文翻译：

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温度和多种寄生虫结合改变寄主群落结构

预测气候变化的影响需要了解多种非生物和生物因素之间的复杂相互作用。通过影响宿主物种之间的关键相互作用，寄生虫可以影响群落和生态系统结构。然而，我们对多种寄生虫和非生物因素如何相互作用以改变生态系统结构的理解仍然有限。为了凭经验测试温度变化和寄生虫在塑造群落中的作用，我们使用了由四种同域淡水甲壳类动物（等足类和片脚类动物）组成的多代中胚层实验，这些物种共享多达四种寄生虫。中胚层被分配到四种不同处理中的一种，具有不同的季节性温度（正常和升高）和寄生虫暴露水平（连续和停滞（中胚层中寄生虫幼虫的存在或不存在））。我们发现寄生虫暴露和水温对寄主社区有交互影响。持续接触寄生虫改变了群落结构，水温的差异改变了物种丰度。片脚类动物的丰富度当经历持续的寄生虫暴露和升高的水温时，Paracalliope fluviatilis显着减少。高温还导致另一种片脚类宿主Paracorophium excavatum 中寄生虫引起的死亡. 相比之下，等足类宿主受到的影响要小得多，这表明温度升高以及寄生虫暴露的增加可能会增加它们在社区中的相对丰度。无脊椎动物宿主种群的变化对其他物种（如食用甲壳类动物的鱼类和鸟类）产生影响，并对生态系统过程产生影响，如水生初级生产和养分循环。根据气候变化预测，寄生虫暴露和平均气温上升可能对社区和生态系统产生重大影响，改变生态系统结构和动态。