Department of Ecology and Ecosystem Modeling, Institute of Biochemistry and Biology, University of Potsdam, Maulbeerallee 2, Potsdam, 14469, Germany.
Ecology. 2020 May;101(5):e02995. doi: 10.1002/ecy.2995. Epub 2020 Feb 28.
The competitive exclusion principle is one of the oldest ideas in ecology and states that without additional self-limitation two predators cannot coexist on a single prey. The search for mechanisms allowing coexistence despite this has identified niche differentiation between predators as crucial: without this, coexistence requires the predators to have exactly the same R* values, which is considered impossible. However, this reasoning misses a critical point: predators' R* values are not static properties, but affected by defensive traits of their prey, which in turn can adapt in response to changes in predator densities. Here I show that this feedback between defense and predator dynamics enables stable predator coexistence without ecological niche differentiation. Instead, the mechanism driving coexistence is that prey adaptation causes defense to converge to the value where both predators have equal R* values ("fitness equalization"). This result is highly general, independent of specific model details, and applies to both rapid defense evolution and inducible defenses. It demonstrates the importance of considering long-standing ecological questions from an eco-evolutionary viewpoint, and showcases how the effects of adaptation can cascade through communities, driving diversity on higher trophic levels. These insights offer an important new perspective on coexistence theory.
竞争排斥原理是生态学中最古老的概念之一，它指出如果没有其他自我限制因素，两个捕食者不可能在同一猎物上共存。尽管如此，人们仍在寻找允许共存的机制，这些机制确定了捕食者之间的生态位分化至关重要：如果没有这种分化，共存就要求捕食者的 R* 值完全相同，这被认为是不可能的。然而，这种推理忽略了一个关键要点：捕食者的 R* 值不是静态属性，而是受到猎物防御特征的影响，而猎物反过来又可以适应捕食者密度的变化。在这里，我表明这种防御和捕食者动态之间的反馈可以在没有生态位分化的情况下实现稳定的捕食者共存。相反，驱动共存的机制是，猎物的适应导致防御趋同于两个捕食者具有相等 R* 值的那个值（“适应值均等化”）。这个结果具有高度的普遍性，不依赖于特定的模型细节，并且适用于快速防御进化和诱导防御。它证明了从生态进化观点考虑长期存在的生态问题的重要性，并展示了适应的影响如何通过群落级联，在更高营养级驱动多样性。这些观点为共存理论提供了一个新的重要视角。
