Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA.
Am Nat. 2013 Aug;182(2):E25-39. doi: 10.1086/670810. Epub 2013 Jun 20.
Herbivores eat the leaves that a plant needs for photosynthesis. However, the degree of antagonism between plant and herbivore may depend critically on the timing of their interactions and the intrinsic value of a leaf. We present a model that investigates whether and when the timing of plant defense and herbivore feeding activity can be optimized by evolution so that their interactions can move from antagonistic to neutral. We assume that temporal changes in environmental conditions will affect intrinsic leaf value, measured as potential carbon gain. Using optimal-control theory, we model herbivore evolution, first in response to fixed plant strategies and then under coevolutionary dynamics in which the plant also evolves in response to the herbivore. In the latter case, we solve for the evolutionarily stable strategies of plant defense induction and herbivore hatching rate under different ecological conditions. Our results suggest that the optimal strategies for both plant and herbivore are to avoid direct conflict. As long as the plant has the capability for moderately lethal defense, the herbivore will modify its hatching rate to avoid plant defenses, and the plant will never have to use them. Insights from this model offer a possible solution to the paradox of sublethal defenses and provide a mechanism for stable plant-herbivore interactions without the need for natural enemy control.
食草动物会吃掉植物进行光合作用所需的叶子。然而，植物和食草动物之间的拮抗程度可能取决于它们相互作用的时间以及叶子的内在价值。我们提出了一个模型，用于研究植物防御和食草动物取食活动的时间是否以及何时可以通过进化进行优化，从而使它们的相互作用从拮抗转变为中性。我们假设环境条件的时间变化会影响内在叶子价值，以潜在碳增益来衡量。我们使用最优控制理论，首先在固定植物策略的情况下模拟食草动物的进化，然后在植物也对食草动物进化做出响应的共进化动态下模拟食草动物的进化。在后一种情况下，我们针对不同生态条件下植物防御诱导和食草动物孵化率的进化稳定策略进行求解。我们的结果表明，植物和食草动物的最优策略是避免直接冲突。只要植物具有中等致死防御的能力，食草动物就会调整其孵化率以避免植物防御，而植物则无需使用防御。该模型提供的见解为亚致死防御的悖论提供了一个可能的解决方案，并为无需使用天敌控制就能实现稳定的植物-食草动物相互作用提供了一种机制。
