Understanding microbial roles in ecosystem function requires integrating microscopic processes into food webs. The carnivorous pitcher plant, Sarracenia purpurea, offers a tractable study system where diverse food webs of macroinvertebrates and microbes facilitate digestion of captured insect prey, releasing nutrients supporting the food web and host plant. However, how interactions between these macroinvertebrate and microbial communities contribute to ecosystem functions remains unclear. We examined the role of the pitcher plant mosquito, Wyeomyia smithii, in top-down control of the composition and function of pitcher plant microbial communities. Mosquito larval abundance was enriched or depleted across a natural population of S. purpurea pitchers over a 74-day field experiment. Bacterial community composition and microbial community function were characterized by 16S rRNA amplicon sequencing and profiling of carbon substrate use, bulk metabolic rate, hydrolytic enzyme activity, and macronutrient pools. Bacterial communities changed from pitcher opening to maturation, but larvae exerted minor effects on high-level taxonomic composition. Higher larval abundance was associated with lower diversity communities with distinct functions and elevated nitrogen availability. Treatment-independent clustering also supported roles for larvae in curating pitcher microbial communities through shifts in community diversity and function. These results demonstrate top-down control of microbial functions in an aquatic microecosystem.

中文翻译：

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蚊子调节水生微生态系统中的微生物多样性和功能

了解微生物在生态系统功能中的作用需要将微观过程整合到食物网中。肉食性猪笼草提供了一个易于处理的研究系统，其中大型无脊椎动物和微生物的不同食物网促进捕获的昆虫猎物的消化，释放支持食物网和寄主植物的营养物质。然而，这些大型无脊椎动物和微生物群落之间的相互作用如何促进生态系统功能仍不清楚。我们研究了猪笼草蚊子Wyeomyia smithii在自上而下控制猪笼草微生物群落的组成和功能中的作用。在为期 74 天的田间实验中，紫斑蚊自然种群中的蚊子幼虫丰度有所增加或减少。通过 16S rRNA 扩增子测序和碳底物使用、总体代谢率、水解酶活性和大量营养素库的分析来表征细菌群落组成和微生物群落功能。细菌群落从瓶口开放到成熟发生了变化，但幼虫对高级分类组成的影响较小。较高的幼虫丰度与具有独特功能和较高氮利用率的较低多样性群落相关。独立于处理的聚类还支持幼虫通过改变群落多样性和功能来管理猪笼草微生物群落的作用。这些结果证明了水生微生态系统中微生物功能的自上而下的控制。