Selection for intermediate mortality and reproduction rates in a spatiallystructured population

How local interactions influence both population and evolutionary dynamics is currently a key topic in theoretical ecology. We use a 'well-mixed' anal ytical model and spatially explicit individual-based models to investigate a system where a population is subject to rare disturbance events. The dist urbance can only propagate through regions of the population where the dens ity of individuals is sufficiently high and individuals affected by the dis turbance die shortly after. We find that populations where individuals are sessile often exhibit very different dynamic behaviour when compared to pop ulations where individuals are mobile and spatially well mixed. When mutati ons are allowed which affect either offspring birth rates or mortality rate s, the well-mixed populations always evolve to a state where a single distu rbance event leads to extinction. Populations often persist substantially l onger if individuals are sessile and they disperse their offspring locally. We also find that for sessile populations selection may favour short-lived individuals with limited offspring production. Population dynamics are fou nd to be strongly influenced by the host characters that are evolving and t he rate at which host variation is introduced into the system.