Transitions between male and female heterogamety caused by sex-antagonistic selection.
Many animal taxa show frequent and rapid transitions between male heterogamety (XY) and female heterogamety (ZW). We develop a model showing how these transitions can be driven by sex-antagonistic selection. Sex-antagonistic selection acting on loci linked to a new sex-determination mutation can cause it to invade, but when acting on loci linked to the ancestral sex-determination gene will inhibit an invasion. The strengths of the consequent indirect selection on the old and new sex-determination loci are mediated by the strengths of sex-antagonistic selection, linkage between the sex-antagonistic and sex-determination genes, and the amount of genetic variation. Sex-antagonistic loci that are tightly linked to a sex-determining gene have a vastly stronger influence on the balance of selection than more distant loci. As a result, changes in linkage, caused, for example, by an inversion that captures a sex-determination mutation and a gene under sex-antagonistic selection, can trigger transitions between XY and ZW systems. Sex-antagonistic alleles can become more strongly associated with pleiotropically dominant sex-determining factors, which may help to explain biases in the rates of transitions between male and female heterogamety. Deleterious recessive mutations completely linked to the ancestral Y chromosome can prevent invasion of a neo-W chromosome or result in a stable equilibrium at which XY and ZW systems segregate simultaneously at two linkage groups.
van Doorn
G Sander
GS
Section of Integrative Biology C-0930, University of Texas, Austin, TX 78712, USA. sander.vandoorn@iee.unibe.ch
Kirkpatrick
Mark
M
D000483:Alleles; D000818:Animals; D004843:Epistasis, Genetic; D005260:Female; D008040:Genetic Linkage; D014644:Genetic Variation; D005854:Germ Cells; D008297:Male; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes