Koffel Thomas, Daufresne Tanguy, Massol François, Klausmeier Christopher A
Am Nat. 2018 Sep;192(3):360-378. doi: 10.1086/698600. Epub 2018 Jul 12.
Plants present a variety of defensive strategies against herbivores, broadly classified into tolerance and resistance. Since resource availability can also limit plant growth, we expect plant allocation to resource acquisition and defense to vary along resource gradients. Yet, the conditions under which one defensive strategy is favored over the other are unclear. Here, we use an eco-evolutionary model to investigate plant adaptive allocation to resource acquisition, tolerance, and resistance along a resource gradient in a simple food web module inspired by plankton communities where plants compete for a single resource and are grazed on by a shared herbivore. We show that undefended, acquisition-specialist strategies dominate under low resource supplies. Conversely, high resource supplies, which lead to high herbivore abundance because of trophic transfers, result in either the dominance of very resistant strategies or coexistence between a completely resistant strategy and a fast-growing, tolerant one. We also explore the consequences of this adaptive allocation on species biomasses. Finally, we compare our predictions to a more traditional, density-independent optimization model. We show that density dependence mediated by resources and herbivores is the cause of the increase in plant resistance along the resource gradient, as the optimization model would instead have favored tolerance.
植物针对食草动物展现出多种防御策略，大致可分为耐受性和抗性。由于资源可用性也会限制植物生长，我们预期植物在资源获取和防御方面的分配会随资源梯度而变化。然而，一种防御策略比另一种更受青睐的条件尚不清楚。在此，我们使用一个生态进化模型，在一个受浮游生物群落启发的简单食物网模块中，沿着资源梯度研究植物对资源获取、耐受性和抗性的适应性分配，在这个模块中植物竞争单一资源并被一种共享的食草动物啃食。我们表明，在低资源供应情况下，无防御的、获取资源型的策略占主导。相反，高资源供应由于营养级传递导致食草动物数量众多，要么导致抗性极强的策略占主导地位，要么导致完全抗性的策略与快速生长的耐受性策略共存。我们还探讨了这种适应性分配对物种生物量的影响。最后，我们将我们的预测结果与一个更传统的、与密度无关的优化模型进行比较。我们表明，由资源和食草动物介导的密度依赖性是植物抗性沿资源梯度增加的原因，因为优化模型反而会更青睐耐受性。
