R codes and their outputs used for: Evolution of realised niche breadth diversity driven by community dynamics

Why many herbivorous insects are host-plant specialists, with non-negligible exceptions, is a conundrum of evolutionary biology, especially because the host plants are not necessarily optimal larval diets. Here, I present a novel model of host-plant preference evolution of two insect species. Because habitat preference evolution is contingent upon demographic dynamics, I integrate the evolutionary framework with the modern coexistence theory. The results show that the two insect species can evolve into a habitat specialist and generalist when they experience both negative and positive frequency-dependent community dynamics. This happens because the joint action of positive and negative frequency dependence creates multiple (up to nine) eco-evolutionary equilibria. Furthermore, initial condition dependence due to positive frequency dependence allows specialization to poor habitats. Thus, evolved habitat preferences do not necessarily correlate with the performances. The model provides explanations for counterintuitive empirical patterns and mechanistic interpretations for phenomenological models of niche breadth evolution.

Methods
Individual based (i.e., stochastic) model of eco-evolutionary dynamics. The simulations were run on a 32-cored Win machine. Memory capacity of 32 GB will be sufficient.

为何多数植食性昆虫均为寄主植物专性类群，却又存在诸多不容忽视的特例，这一直是进化生物学领域的一大未解难题——尤其值得注意的是，寄主植物未必是幼虫的最优食谱。本文针对两种昆虫的寄主偏好进化过程，提出了一种全新的理论模型。由于生境偏好的进化过程依赖于种群动态，因此本文将进化理论框架与现代共存理论相结合。研究结果显示：当两种昆虫同时受到负频率依赖与正频率依赖的群落动态作用时，它们可分别进化为生境专性物种与广适性物种。这一现象的成因在于，正、负频率依赖的共同作用可产生多达9种生态-进化均衡点。此外，由正频率依赖所带来的初始条件依赖性，可使物种特化于贫瘠生境。由此可见，进化形成的生境偏好未必与物种的适合度表现相关联。本模型既为诸多反直觉的经验研究模式提供了理论解释，也为生态位宽度进化的现象学模型提供了机理性阐释。

研究方法
本文采用基于个体的（即随机）生态-进化动态模型。模拟程序运行于一台32核Windows工作站，32 GB的内存容量即可满足需求。