Ecosystem degradation due to anthropogenic activities is the primary issue of our times. Theoretical analyses as well as efforts to restore and manage ecosystems depend on comprehensive metrics of ecosystem function. In the case of complex ecosystems such as tropical coral reefs—especially where monitoring, management, and restoration are important—multiple metrics reflecting key functional groups are required to accurately reflect ecosystem function and when necessary, diagnose degree and kind of ecosystem degradation. We propose inclusion of the generalist ectoparasite functional group as a measure of ecosystem function of coral reefs. This functional group is adaptable to loss of other community members and may experience an increase in abundance as ecosystem function declines. Fish‐parasitic gnathiid isopods are a member of this group, resident though inconspicuous in coral‐reef communities. On Caribbean coral reefs, based on 938 light‐trap samples, we observed a negative correlation between abundance of smaller‐sized gnathiids and abundance of live coral, a natural predator of gnathiids. Plots grouped by coral cover—a measure of success of the ecosystem engineer—and ectoparasite abundance varied significantly in community composition including abundance of macroalgae, turf algae, and farming Stegastes spp. damselfish reflecting shifts in community structure. Changes in gnathiid abundance with respect to the abundance of organisms participating in each of the core functional processes driving coral‐reef ecosystems reflect broad connectivity of gnathiid parasites across the ecosystem. We conclude that the hyperabundance of a small, cryptic, generalist parasite, when used in combination with a metric of abundance of the primary ecosystem engineer, can provide one nuanced measure of the ecosystem vulnerability to collapse.

中文翻译：

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神秘的通才寄生虫的丰富反映了生态系统的退化

人为活动造成的生态系统退化是我们时代的主要问题。理论分析以及恢复和管理生态系统的努力取决于生态系统功能的综合指标。对于热带珊瑚礁等复杂的生态系统（尤其是在监视，管理和恢复很重要的情况下），需要多个反映关键功能组的指标来准确反映生态系统功能，并在必要时诊断生态系统退化的程度和类型。我们建议将通才外寄生虫功能组包括在内，以衡量珊瑚礁的生态系统功能。该功能组适应于其他社区成员的流失，并且随着生态系统功能的下降，其丰度可能会增加。鱼类寄生的拟南芥等足动物是该组的成员，居民虽然在珊瑚礁社区中不起眼。在基于938个光阱样品的加勒比珊瑚礁上，我们观察到大量小尺寸的拟南芥和天然的捕食类珊瑚活珊瑚之间存在负相关。由珊瑚覆盖物（生态系统工程师的成功程度）和外部寄生虫的丰度分组的群落在群落组成（包括大型藻类，草皮藻类和农业的丰度）方面差异很大Stegastes spp。雀鲷反映了社区结构的变化。关于参与驱动珊瑚礁生态系统的每个核心功能过程的生物体数量的变化，网纹兰种群的丰度变化反映了整个生态系统中网纹兰寄生虫的广泛连通性。我们得出的结论是，将小型，隐蔽，通才寄生虫的丰度与主要生态系统工程师的丰度度量结合使用时，可以提供一种微妙的衡量生态系统崩溃的方法。