Speaker
Description
The existence of an Evolutionarily Stable State (ESS) in a host-symbiont interaction at ecologically stable coexistence is studied in the framework of eco-evolutionary dynamics. Our basic objective is to obtain an evolutionary insight into the transmission behaviour of symbionts (which can be either parasitic or mutualistic depending on effects on mortality and fecundity) which are obligate and host-specific. To address this scenario, a general problem of coexistence of host and symbiont is considered with both vertical and horizontal transmission at the same time. The evolutionary success of the vertically transmitted symbionts is given by the evolutionary success of their infected host lineage. Furthermore, our selection situation belongs to the multi-species group selection models as the symbionts and the host together form a “group”. The novelty of our study is that the dynamics of group formation is not based on interactions between the host and the symbiont, and also that the horizontal infection and clearing of infection are independent. Age-structured population based on the general kin demographic selection with dependence between infected and non-infected lineages is considered. The main idea of this model is that the evolutionarily best phenotype maximizes its phenotypic long-term growth rate. We derive the population dynamics of the system based on this model and find a two-species stable ecological state. For the evolutionary stability of the resident system, we require that each mutation introduced at the stable state will die out by ecological selection. An ecological game between the obligate symbiont and the host, with payoffs dependent on long-term growth rates of the lineages, is also examined at this ecological stable state of the host-symbiont coevolutionary selection dynamics.
