Huang Qihua, Wang Hao, Lewis Mark A
Center for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1.
Center for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1; Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1.
J Theor Biol. 2015 Aug 7;378:12-30. doi: 10.1016/j.jtbi.2015.04.019. Epub 2015 Apr 25.
Predators and prey may be simultaneously exposed to environmental toxins, but one may be more susceptible than the other. To study the effects of environmental toxins on food web dynamics, we develop a toxin-dependent predator-prey model that combines both direct and indirect toxic effects on two trophic levels. The direct effects of toxins typically reduce organism abundance by increasing mortality or reducing fecundity. Such direct effects, therefore, alter both bottom-up food availability and top-down predatory ability. However, the indirect effects, when mediated through predator-prey interactions, may lead to counterintuitive effects. This study investigates how the balance of the classical predator-prey dynamics changes as a function of environmental toxin levels. While high toxin concentrations are shown to be harmful to both species, possibly leading to extirpation of both species, intermediate toxin concentrations may affect predators disproportionately through biomagnification, leading to reduced abundance of predators and increased abundance of the prey. This counterintuitive effect significantly increases biomass at the lower trophic level. Environmental toxins may also reduce population variability by preventing populations from fluctuating around a coexistence equilibrium. Finally, environmental toxins may induce bistable dynamics, in which different initial population levels produce different long-term outcomes. Since our toxin-dependent predator-prey model is general, the theory developed here not only provides a sound foundation for population or community effects of toxicity, but also could be used to help develop management strategies to preserve and restore the integrity of contaminated habitats.
捕食者和猎物可能会同时接触环境毒素，但其中一方可能比另一方更易受影响。为了研究环境毒素对食物网动态的影响，我们构建了一个依赖毒素的捕食者 - 猎物模型，该模型结合了对两个营养级的直接和间接毒性作用。毒素的直接作用通常通过增加死亡率或降低繁殖力来减少生物数量。因此，这种直接作用会改变自下而上的食物可利用性和自上而下的捕食能力。然而，当通过捕食者 - 猎物相互作用介导时，间接作用可能会导致意想不到的效果。本研究调查了经典捕食者 - 猎物动态平衡如何随环境毒素水平而变化。虽然高毒素浓度对两个物种都有害，可能导致两个物种灭绝，但中等毒素浓度可能通过生物放大作用对捕食者产生不成比例的影响，导致捕食者数量减少和猎物数量增加。这种意想不到的效果显著增加了较低营养级的生物量。环境毒素还可能通过阻止种群在共存平衡附近波动来降低种群变异性。最后，环境毒素可能会引发双稳态动态，即不同的初始种群水平会产生不同的长期结果。由于我们的依赖毒素的捕食者 - 猎物模型具有通用性，这里所发展的理论不仅为毒性对种群或群落的影响提供了坚实的基础，还可用于帮助制定管理策略，以保护和恢复受污染栖息地的完整性。
