Selection by parasites for clonal diversity and mixed mating

Abstract

On theoretical grounds, coevolutionary interactions with parasites can select for cross-fertilization, even when there is a twofold advantage gained by reproducing through uniparental (asexual) means. The suspected advantage of cross-fertilization stems from the production of genetically rare offspring, which are expected to be more likely to escape infection by coevolving enemies. The authors consider the effects that parasites have on parthenogenetic mutants in obligately sexual, dioecious populations. Computer simulations show that repeated mutation to parthogenesis can lead to the accumulation of clones with different resistance genotypes, and that a moderately diverse set of clones could competitively exclude the ancestral sexual subpopulation. When there are reasonable rates of deleterious mutation, Muller's ratchet combined with coevolutionary interactions with parasites can lead to the evolutionary stability of cross-fertilization. The effects that parasites can have on the evolution of uniparental reproduction in cosexual populations are also considered. Strategy models show that parasites and inbreeding depression could interact to select for evolutionarily stable reproductive strategies that involve mixtures of selfed and outcrossed progeny. -Authors