Theoretical study of evolutionary mechanisms of polymorphism of anti-herbivore defense in plant

在植物物种的抗食草动物防御中，有时在单个种群中观察到防御水平的遗传多态。从博弈论的角度分析了个体间交互作用的演化过程，以期了解导致个体间交互作用的特征多态的形成机制。我关注的是一个合作博弈，在这个博弈中，个人投资使互动小组的成员受益。分析表明，多态发生的可能性在很大程度上取决于合作的收益函数和成本函数的性质。例如，收益可以是总投资的函数，也可以是每项投资的函数的总和。前者可以进行进化分支和随后的多态进化，而后者则不可能。这项研究成功地揭示了一类合作的进化条件，涉及植物中的反食草动物防御。

In anti-herbivore defenses in plant species, genetic polymorphism of defensive level is sometime observed within a single population. In order to understand mechanisms resulting in the polymorphism of trait that influences interaction among individuals, I analyzed its evolutionary process from a viewpoint of game theory. I focus on a cooperative game, in which an individual investment benefits members of the interacting group. According to the analysis, it is shown that a possibility of occurrence of polymorphism significantly depends on properties of benefit and cost functions of cooperation. For example, the benefit can be a function of the total investments, or a total of functions of each investment. Evolutionary branching and following polymorphism evolution are possible in the former, but impossible in the latter. The study successfully revealed evolutionary conditions of a class of cooperation, involving anti-herbivore defenses in plants.