Soudijn Floor H, de Roos André M
Am Nat. 2017 Dec;190(6):844-853. doi: 10.1086/694119. Epub 2017 Aug 31.
The trophic structure of species communities depends on the energy transfer between trophic levels. Primary productivity varies strongly through time, challenging the persistence of species at higher trophic levels. Yet resource variability has mostly been studied in systems with only one or two trophic levels. We test the effect of variability in resource productivity in a tritrophic model system including a resource, a size-structured consumer, and a size-specific predator. The model complies with fundamental principles of mass conservation and the body-size dependence of individual-level energetics and predator-prey interactions. Surprisingly, we find that resource variability may promote predator persistence. The positive effect of variability on the predator arises through periods with starvation mortality of juvenile prey, which reduces the intraspecific competition in the prey population. With increasing variability in productivity and starvation mortality in the juvenile prey, the prey availability increases in the size range preferred by the predator. The positive effect of prey mortality on the trophic transfer efficiency depends on the biologically realistic consideration of body size-dependent and food-dependent functions for growth and reproduction in our model. Our findings show that variability may promote the trophic transfer efficiency, indicating that environmental variability may sustain species at higher trophic levels in natural ecosystems.
物种群落的营养结构取决于营养级之间的能量传递。初级生产力随时间变化很大，这对较高营养级物种的存续构成挑战。然而，资源变异性大多是在只有一两个营养级的系统中进行研究的。我们在一个三营养级模型系统中测试资源生产力变异性的影响，该系统包括一种资源、一个具有大小结构的消费者和一个特定大小的捕食者。该模型符合质量守恒的基本原理以及个体能量学和捕食者 - 猎物相互作用对体型的依赖性。令人惊讶的是，我们发现资源变异性可能会促进捕食者的存续。变异性对捕食者的积极影响是通过幼年猎物出现饥饿死亡的时期产生的，这减少了猎物种群中的种内竞争。随着生产力变异性和幼年猎物饥饿死亡率的增加，捕食者偏好的大小范围内的猎物可利用性增加。猎物死亡率对营养传递效率的积极影响取决于我们模型中对生长和繁殖的体型依赖性和食物依赖性函数的生物学现实考量。我们的研究结果表明，变异性可能会促进营养传递效率，这表明环境变异性可能会维持自然生态系统中较高营养级的物种。
