A theoretical study of host-parasitoid trait coevolution

Since obligate parasites or predators often severely exploit their hosts or preys, even they cannot live without victims, exploiter-victim interactions are likely to result in evolutionary change of offensive and defensive traits. In such antagonistic interactions, the evolution of one species promotes the counter-evolution of the other, thereby triggering evolutionary exaggeration. Trait coevolution of host-parasitoid is relevant to stable coexistence of population, genetic diversity and speciation or pathogen evolution and prediction of epidemics. In contrast with its importance, however, coevolutionary dynamics arise as a consequence of interactions within an interspecific polymorphism of coevolutionary traits is complex and detecting evolutionary change through population is extremely difficult. Theoretical approaches are suited to explore such a complicated coevolution of host-parasitoid and many theoretical models on arms race have been proposed and have shown that arms race is a possible outcome of many factors (e.g. host productivity, cost of coevolutionary trait) in last several decades. In this seminar I report that the mathematical model of i) the camellia-weevil trait coevolution with empirically estimated parameters and ii) mixed planting strategies of resistant host crops and disease control. In the first section, I mathematically analyzed the coevolution of Japanese camellia and its obligate seed predator weevil. Evolutionary stable analysis predicts the geographical cline of coevolutionary traits is robust outcome when the cost of parasitoid trait is nonlinear (accelerating). In the second section, I discuss the mixed planting of resistant host and the optimal control strategy.