Trophic cascades -- indirect effects of predators that propagate down through food webs -- have been extensively documented. It has also been shown that predator diversity can mediate these trophic cascades, and separately, that herbivore biomass can influence the stability of primary producers. However, whether predator diversity can cause cascading effects on the stability of lower trophic levels has not yet been studied. We conducted a laboratory microcosm experiment and a field mesocosm experiment manipulating the presence and coexistence of two heteropteran predators and measuring their effects on zooplankton herbivores and phytoplankton basal resources. We predicted that if the predators partitioned their zooplankton prey, for example by size, then co-presence of the predators would reduce zooplankton prey mass and lead to 1) increased average values and 2) decreased temporal variability of phytoplankton basal resources. We present evidence that the predators partitioned their zooplankton prey, leading to a synergistic suppression of zooplankton; and that in turn, this suppression of zooplankton reduced the variability of phytoplankton biomass. However, mean phytoplankton biomass was unaffected. Our results demonstrate that predator diversity may indirectly stabilize basal resource biomass via a "diversity-stability trophic cascade," seemingly dependent on predator complementarity, but independent of a classic trophic cascade in which average biomass is altered. Therefore predator diversity, especially if correlated with diversity of prey use, could play a role in regulating ecosystem stability. Furthermore, this link between predator diversity and producer stability has implications for potential biological control methods for improving the reliability of crop yields.

中文翻译：

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捕食者的互补性抑制了多样性-稳定性营养级联中浮游植物生物量的变异性。

营养级联-掠食性动物通过食物网向下传播的间接影响-已被广泛记录。还已经表明，捕食者的多样性可以介导这些营养级联反应，并且食草动物生物量可以分别影响初级生产者的稳定性。但是，尚未研究捕食者的多样性是否能对较低营养水平的稳定性造成连锁效应。我们进行了实验室缩影实验和田间中观实验，以控制两种异翅类天敌的存在和共存，并测量它们对浮游植物食草动物和浮游植物基础资源的影响。我们预测，如果捕食者按大小划分其浮游动物猎物，那么捕食者的并存会减少浮游动物的猎物质量，并导致1）平均值增加和2）浮游植物基础资源的时间变异性降低。我们提供的证据表明，捕食者划分了其浮游动物的猎物，从而导致了对浮游动物的协同抑制。反过来，这种对浮游动物的抑制作用降低了浮游植物生物量的变异性。然而，浮游植物的平均生物量不受影响。我们的结果表明，捕食者的多样性可能通过“多样性-稳定性营养级联”间接稳定基础资源生物量，看似依赖于捕食者的互补性，但独立于经典的营养级联，在该级联中平均生物量发生了变化。因此，捕食者的多样性，尤其是与猎物使用的多样性相关时，可以在调节生态系统稳定性方面发挥作用。此外，捕食者多样性与生产者稳定性之间的这种联系对于提高作物产量可靠性的潜在生物防治方法具有重要意义。