EVOLUTIONARY CONSEQUENCES OF CYTOPLASMICALLY INHERITED FEMINIZING FACTORS

We develop a model to analyse the population and evolutionary consequences of parasitic sex ratio distortion to a particular class of systems, where the sex ratio organism (SRO) acts on host sex ratio by converting genotypic males into phenotypic females. Our model differs from previous approaches in that we explicitly distinguish between the processes of SRO transmission (infection) and sRo expression (SRO-induced feminization). We conclude that the evolutionarily stable host sex ratio will be biased towards the non-transmitting sex, provided that the sRo transmission and feminization efficiencies are not both 100%. Feedback between SRO prevalence and host sex ratio may drive to monogeny (the situation in which uninfected hosts produce only the non-transmitting sex). However, for many combinations of transmission and feminization efficiency, this feedback interaction does not lead to the exclusive production of males by uninfected females.