EFFECTS OF RHYTHMIC REPRODUCTION ON THE SURVIVAL OF COOPERATORS

Organisms on Earth are known to evolve by cooperating with their neighbors in external environments. These cooperating organisms are under the influence of circadian rhythms derived from Earth's rotation and have various biological rhythms within them. However, little is known about the effects of these rhythms on the cooperation of organisms. In this study, we investigate the effects of the biological rhythms on the survival of cooperators in evolution using evolutionary game theory. We focused on the rhythm in reproduction among the various biological rhythms that organisms have. Our results are as follows. Rhythmic reproductions play a role in limiting the survival of cooperators; they reduce the survival limits of cooperators compared to when there is no rhythm. Their limiting force is sensitive to the number of interacting neighbors, however. When the number of interacting neighbors is relatively small, the effects of rhythm in reproduction on the survival limits of cooperators are not significant. As the number of interacting neighbors increases, the limiting force of rhythmic reproductions becomes more powerful, gradually decreasing the survival limits of cooperators. Variations of rhythm in reproduction do not alter the survival limits; they only cause fluctuations in the population of cooperators within the survival limits. Our findings suggest that the rhythmic reproductions in evolution determine the survival domain of cooperators, where the number of interacting neighbors is a major factor along with rhythmic reproductions. Organisms under the constant pressure imposed by rhythmic reproductions may need to find the optimal number of interacting neighbors to survive and evolve to a new level through cooperation.