Evolution of sex-determining mechanisms in a wild population of armadillidium vulgare latr. (crustacea, isopoda): Competition between two feminizing parasitic sex factors

Abstract

Sex determination in A. vulgare may be under the control of two maternally transmitted parasitic sex factors (PSF) that reverse genetic males (ZZ) into functional neo-females. The first PSF is a Wolbachia-like bacterium (F) and the other (f) is probably a sequence of the F bacterial DNA unstably integrated into the host genome. In the Niort population (France), where these two PSF are mixed, the frequency of neo-females harbouring/increased over a period of 23 years, at the expense of neo-females harbouring F. As the maternal transmission to offspring is higher for F than for f, the evolution of the F/f ratio disagrees with theoretical models involving a cytoplasmic factor. We show that an autosomal masculinizing gene (M) allows a high rate of paternal transmission of f, which could explain the spread of this factor in the population. © The Genetical Society of Great Britain.