EVOLUTIONARY CONSEQUENCES OF CYTOPLASMICALLY INHERITED FEMINIZING FACTORS

We develop a model to analyse the population and evolutionary conseque nces of parasitic sex ratio distortion to a particular class of system s, where the sex ratio organism (SRO) acts on host sex ratio by conver ting genotypic males into phenotypic females. Our model differs from p revious approaches in that we explicitly distinguish between the proce sses of SRO transmission (infection) and sRo expression (SRO-induced f eminization). We conclude that the evolutionarily stable host sex rati o will be biased towards the non-transmitting sex, provided that the s Ro transmission and feminization efficiencies are not both 100%. Feedb ack between SRO prevalence and host sex ratio may drive to monogeny (t he situation in which uninfected hosts produce only the non-transmitti ng sex). However, for many combinations of transmission and feminizati on efficiency, this feedback interaction does not lead to the exclusiv e production of males by uninfected females.