Biodiversity is typically considered as a one-dimensional metric (e.g. species richness), yet the consequences of species loss may be different depending on where extinctions occur in the food web. Here, I used a manipulative field experiment in a temperate subtidal marine system to explore the implications of diversity loss at multiple trophic levels for ecosystem functioning and food web structure. The four manipulated predators included the small painted goby and common prawn, which are also fed on by the larger black goby and shore crab. Antagonistic interactions between the manipulated predators (e.g. intraguild predation, intimidation, interference competition) limited their negative effects on the rest of the food web. Top-down control was so suppressed at the highest level of multitrophic diversity that the resulting food webs were as complex and productive as those containing no manipulated predators. Negative interactions between the predators weakened as multitrophic diversity decreased, however, resulting in stronger consumption of lower trophic levels and a simpler food web with lower rates of two key ecosystem processes: primary production and decomposition. These results show how indirect interactions between predators on multiple trophic levels help to promote the complexity and functioning of natural systems.

中文翻译：

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多营养多样性通过抑制浅层海洋底栖食物网的自上而下控制来维持生态复杂性

生物多样性通常被视为一维指标（例如物种丰富度），但物种丧失的后果可能因食物网中发生灭绝的位置而异。在这里，我在温带潮下带海洋系统中使用了一个操纵性现场实验，以探索多样性丧失在多个营养级别对生态系统功能和食物网结构的影响。四种被操纵的捕食者包括小型彩绘虾虎鱼和普通虾，它们也以较大的黑虾虎鱼和岸蟹为食。被操纵的捕食者之间的对抗性相互作用（例如行内捕食、恐吓、干扰竞争）限制了它们对食物网其余部分的负面影响。自上而下的控制在多营养多样性的最高水平上受到如此抑制，以至于由此产生的食物网与那些不包含被操纵的捕食者的食物网一样复杂和富有成效。然而，随着多营养多样性的减少，捕食者之间的负面相互作用减弱，导致对低营养级的更多消耗和更简单的食物网，两个关键生态系统过程的速率较低：初级生产和分解。这些结果表明，捕食者在多个营养级别上的间接相互作用如何有助于促进自然系统的复杂性和功能。导致对较低营养级的更多消耗和更简单的食物网，两个关键生态系统过程的速率较低：初级生产和分解。这些结果表明，捕食者在多个营养级别上的间接相互作用如何有助于促进自然系统的复杂性和功能。导致对较低营养级的更多消耗和更简单的食物网，两个关键生态系统过程的速率较低：初级生产和分解。这些结果表明，多个营养级别的捕食者之间的间接相互作用如何有助于促进自然系统的复杂性和功能。