Neural Computation Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
PLoS One. 2014 Apr 9;9(4):e93622. doi: 10.1371/journal.pone.0093622. eCollection 2014.
Polymorphism has fascinated evolutionary biologists since the time of Darwin. Biologists have observed discrete alternative mating strategies in many different species. In this study, we demonstrate that polymorphic mating strategies can emerge in a colony of hermaphrodite robots. We used a survival and reproduction task where the robots maintained their energy levels by capturing energy sources and physically exchanged genotypes for the reproduction of offspring. The reproductive success was dependent on the individuals' energy levels, which created a natural trade-off between the time invested in maintaining a high energy level and the time invested in attracting mating partners. We performed experiments in environments with different density of energy sources and observed a variety in the mating behavior when a robot could see both an energy source and a potential mating partner. The individuals could be classified into two phenotypes: 1) forager, who always chooses to capture energy sources, and 2) tracker, who keeps track of potential mating partners if its energy level is above a threshold. In four out of the seven highest fitness populations in different environments, we found subpopulations with distinct differences in genotype and in behavioral phenotype. We analyzed the fitnesses of the foragers and the trackers by sampling them from each subpopulation and mixing with different ratios in a population. The fitness curves for the two subpopulations crossed at about 25% of foragers in the population, showing the evolutionary stability of the polymorphism. In one of those polymorphic populations, the trackers were further split into two subpopulations: (strong trackers) and (weak trackers). Our analyses show that the population consisting of three phenotypes also constituted several stable polymorphic evolutionarily stable states. To our knowledge, our study is the first to demonstrate the emergence of polymorphic evolutionarily stable strategies within a robot evolution framework.
自从达尔文时代以来，多态性就一直吸引着进化生物学家的注意。生物学家在许多不同的物种中观察到了离散的替代交配策略。在这项研究中，我们证明了多态交配策略可以在一个雌雄同体机器人群体中出现。我们使用了一个生存和繁殖任务，其中机器人通过捕获能源并物理交换基因型来维持能量水平，从而繁殖后代。繁殖成功取决于个体的能量水平，这在维持高能量水平所投入的时间和吸引交配伙伴所投入的时间之间创造了一个自然的权衡。我们在具有不同能源密度的环境中进行了实验，并观察到当机器人可以看到能源和潜在的交配伙伴时，交配行为的多样性。个体可以分为两种表型：1）觅食者，它总是选择捕获能源，2）跟踪者，如果其能量水平高于阈值，则会跟踪潜在的交配伙伴。在七个不同环境中最高适应度的四个群体中，我们发现了在基因型和行为表型上存在明显差异的亚群体。我们通过从每个亚群体中取样并以不同比例混合在一个群体中，分析了觅食者和跟踪者的适应度。两个亚群体的适应度曲线在群体中约有 25%的觅食者处交叉，显示了多态性的进化稳定性。在其中一个多态群体中，跟踪者进一步分为两个亚群体：（强跟踪者）和（弱跟踪者）。我们的分析表明，由三个表型组成的群体也构成了几个稳定的多态进化稳定状态。据我们所知，我们的研究是第一个在机器人进化框架内证明多态进化稳定策略出现的研究。
