title: Conflict over condition-dependent sex allocation can lead to mixed sex-determination systems.
abstract: Theory suggests that genetic conflicts drive turnovers between sex-determining mechanisms, yet these studies only apply to cases where sex allocation is independent of environment or condition. Here, we model parent-offspring conflict in the presence of condition-dependent sex allocation, where the environment has sex-specific fitness consequences. Additionally, one sex is assumed to be more costly to produce than the other, which leads offspring to favor a sex ratio less biased toward the cheaper sex in comparison to the sex ratio favored by mothers. The scope for parent-offspring conflict depends on the relative frequency of both environments: when one environment is less common than the other, parent-offspring conflict can be reduced or even entirely absent, despite a biased population sex ratio. The model shows that conflict-driven invasions of condition-independent sex factors (e.g., sex chromosomes) result either in the loss of condition-dependent sex allocation, or, interestingly, lead to stable mixtures of condition-dependent and condition-independent sex factors. The latter outcome corresponds to empirical observations in which sex chromosomes are present in organisms with environment-dependent sex determination. Finally, conflict can also favor errors in environmental perception, potentially resulting in the loss of condition-dependent sex allocation without genetic changes to sex-determining loci.
authors.affiliation: Theoretical Biology Group, Centre for Evolutionary and Ecological Studies, University of Groningen, the Netherlands; ComPLEX, Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, London, United Kingdom; Department of Genetics, Evolution and Environment, University College London, London, United Kingdom. a.kuijper@ucl.ac.uk.
authors.forename: Bram
authors.initials: B
authors.lastname: Kuijper
authors.forename: Ido
authors.initials: I
authors.lastname: Pen
mesh_terms: D000818:Animals; D003198:Computer Simulation; D004777:Environment; D005260:Female; D008297:Male; D008954:Models, Biological; D019849:Sex Determination Processes; D012744:Sex Ratio; D015053:Zygote / Q000378:metabolism
keywords: Genetic conflict; heterogamety; parent-offspring conflict; sex chromosomes; sex determination; sex ratios, temperature