The effect of population subdivision on the rate of spread of parasite-mediated cytoplasmic incompatibility.

Over 20 species of arthropods are known to harbor an endosymbiotic bacterium, Wolbachia associated with partial reproductive incompatibility. The micro-organism spreads through a random mating population with positive frequency dependence. Many insect populations, however, are subdivided to some degree. In this paper we model the effect of population subdivision on the rate of spread of Wolbachia and show that it slows the rate of spread of the micro-organism but by itself cannot cause a stable polymorphism. The effects of the micro-organism on host fitness, partial incompatibility, and environmental curing are also investigated, both for panmictic and subdivided populations. In all cases, population subdivision slows the rate of spread relative to a panmictic population, but does not produce a stable polymorphism of infection.