Department of Integrative Biology, University of Texas at Austin, Austin, Texas, 78712, USA.
Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, 78712, USA.
Ecology. 2021 Dec;102(12):e03534. doi: 10.1002/ecy.3534. Epub 2021 Oct 7.
Trophic cascades - indirect effects of predators that propagate down through food webs - have been extensively documented in many ecosystem types. 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 the co-presence of the predators would reduce zooplankton prey mass and lead to (1) increased biomass of, 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. In turn, this enhanced zooplankton suppression led to only a weak, non-significant increase in the central tendency of phytoplankton biomass, but significantly reduced its variability. Our results demonstrate that predator diversity may indirectly stabilize basal resource biomass via a "diversity-stability trophic cascade," seemingly dependent on predator complementarity, even when there is no significant classic trophic cascade altering the central tendency of biomass. Therefore predator diversity, especially if correlated with diversity of prey use, could play a role in regulating ecosystem stability. This link between predator diversity and producer stability has implications for conservation and for potential biological control methods to improve crop yield reliability.
营养级联——捕食者通过食物网向下传播的间接影响——在许多生态系统类型中都有广泛的记录。研究还表明，捕食者多样性可以调节这些营养级联，并且食草动物生物量可以影响初级生产者的稳定性。然而，捕食者多样性是否会对较低营养级的稳定性产生级联效应尚未得到研究。我们进行了实验室微宇宙实验和野外中宇宙实验，操纵两种半翅目捕食者的存在和共存，并测量它们对浮游动物食草动物和浮游植物基础资源的影响。我们预测，如果捕食者对其浮游动物猎物进行了分区，例如按大小分区，那么捕食者的共存将减少浮游动物猎物的质量，并导致（1）浮游植物基础资源的生物量增加，和（2）减少浮游植物基础资源的时间可变性。我们提供的证据表明，捕食者对其浮游动物猎物进行了分区，从而协同抑制了浮游动物。反过来，这种增强的浮游动物抑制作用仅导致浮游植物生物量中心趋势的微弱、无显著增加，但显著降低了其可变性。我们的结果表明，捕食者多样性可能通过“多样性-稳定性营养级联”间接稳定基础资源生物量，这种关系似乎依赖于捕食者的互补性，即使没有改变生物量中心趋势的经典营养级联。因此，捕食者多样性，特别是如果与猎物利用多样性相关，可能在调节生态系统稳定性方面发挥作用。捕食者多样性与生产者稳定性之间的这种联系对保护和潜在的生物控制方法以提高作物产量的可靠性具有重要意义。
