Theoretical Studies on Population Dynamics and Adaptive Evolution

I have studied problems on theoretical ecology, specially analyzing mechanisms of population fluctuation by differential equations and investigating adaptive significance of foraging and mating behaviorsof animals by evolutionary game theory. My recent interests are 'evolution of mutualism' and 'interaction between plants and animals' . As far as mutualistic symbiosis, I have explored a mathematical model, applicable for digestive and intracellular symbioses, and identified two factors, vertical transmission from parent hosts to their offspring and utilization of disuse of each other, as important conditions forevolution of mutualistic symbiosis. I am now studying evolutionary process of symbiosis without vertical transmission, for example, mycorrhiza and photo synthetic symbionts in corals.

Plants conduct physical and chemical defenses against insects and herbivorous animals. It is pointed out that plants increase defense efforts when they are apparent for herbivores (Feeny's theory) or when there are not enough resources (Coley's theory). Unifying these two theories, I have developed a model of optimal resource allocation between growth and defense. I am also constructing a theory which explains diversity of defense strategies, for example, chemicaldirect defense or indirect defense using natural enemies, and constitutive defense or induced defense after attack of herbivores.