Despite the fact that native species of amphipods have been recognized as active predators similarly to invasive species, little is known about their predatory impact on aquatic communities. In this study, we used a laboratory experiment, a field enclosure experiment, and an analysis of natural community data to demonstrate how Gammarus fossarum affects the species composition of benthic communities by imposing survival selection on its prey. Our laboratory single-prey experiment brought a clear evidence that tube-less chironomids are vulnerable prey and that the predation rate on the tube-dwelling chironomids decreases with increasing tube toughness (from the soft tubes made of detritus to the hard tubes made of sand or calcium carbonate grains). We found that the introduction of G. fossarum to field enclosures significantly changed the species composition of a macroinvertebrate community at an experimental spring fen site. The soft-bodied, slow moving, and tube-less taxa were depleted the most. It appears that the observed patterns were a result of predator’s preference rather than encounter rate. Survival selection was detected also in natural communities across a large spatial scale. In accordance with the experiments, high densities of G. fossarum limited the proportion or abundance of vulnerable prey. Our study (1) provides the first convincing evidence that biotic interactions have a structuring effect on the spring fen communities, (2) documents how the predatory effect in a community depends on an interplay between the prey handling behaviour of the predator and species-specific susceptibility of prey, and (3) shows that an omnivorous native amphipod may have a strong impact on aquatic communities despite it is regarded less aggressive than its invasive relatives.

中文翻译：

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原始伽马鲁斯镰刀菌影响大型无脊椎动物群落的物种组成：来自实验室，田间环境和自然栖息地的证据

尽管事实证明两栖动物的本地物种与入侵物种相似，是活跃的捕食者，但对其掠食性对水生群落的影响知之甚少。在这项研究中，我们使用了实验室实验，野外围栏实验以及对自然群落数据的分析，以证明伽玛鲁斯镰刀鱼如何通过对捕食者施加生存选择来影响底栖动物群落的物种组成。我们的实验室单一猎物实验提供了明确的证据，说明无管的拟虫是易受伤害的猎物，并且管上的拟虫的捕食率会随着管的韧性增加而降低（从碎屑制成的软管到沙粒或沙子制成的硬管）碳酸钙颗粒）。我们发现引入了G. fossarum到田间围栏，大大改变了春季芬芬实验点大型无脊椎动物群落的物种组成。体弱，动作缓慢和无管类群的消耗最多。看来，观察到的模式是掠食者偏好而不是遭遇率的结果。在大范围的自然社区中也发现了生存选择。根据实验，高密度的G. fossarum限制了脆弱猎物的比例或数量。我们的研究（1）提供了第一个令人信服的证据，表明生物相互作用对春粉群落具有结构性作用；（2）记录了群落中的掠食效应如何取决于捕食者与特定物种之间的食饵行为之间的相互作用（3）表明，杂食性两栖动物可能对水生生物有很大的影响，尽管它被认为比其侵入性亲属的攻击力小。