title: Maintenance of polygenic sex determination in a fluctuating environment: an individual-based model.
abstract: R. A. Fisher predicted that individuals should invest equally in offspring of both sexes, and that the proportion of males and females produced (the primary sex ratio) should evolve towards 1:1 when unconstrained. For many species, sex determination is dependent on sex chromosomes, creating a strong tendency for balanced sex ratios, but in other cases, multiple autosomal genes interact to determine sex. In such cases, the maintenance of multiple sex-determining alleles at multiple loci and the consequent among-family variability in sex ratios presents a puzzle, as theory predicts that such systems should be unstable. Theory also predicts that environmental influences on sex can complicate outcomes of genetic sex determination, and that population structure may play a role. Tigriopus californicus, a copepod that lives in splash-pool metapopulations and exhibits polygenic and environment-dependent sex determination, presents a test case for relevant theory. We use this species as a model for parameterizing an individual-based simulation to investigate conditions that could maintain polygenic sex determination. We find that metapopulation structure can delay the degradation of polygenic sex determination and that periods of alternating frequency-dependent selection, imposed by seasonal fluctuations in environmental conditions, can maintain polygenic sex determination indefinitely.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.|Department of Biology, University of Victoria, Victoria, BC, Canada.
authors.forename: A W
authors.identifier: 0000-0001-6259-6864
authors.initials: AW
authors.lastname: Bateman
authors.affiliation: Department of Biology, University of Victoria, Victoria, BC, Canada.|Bamfield Marine Sciences Centre, Bamfield, BC, Canada.
authors.forename: B R
authors.initials: BR
authors.lastname: Anholt
mesh_terms: D000818:Animals; D033342:Copepoda; D004777:Environment; D005260:Female; D008297:Male; D020412:Multifactorial Inheritance; D012730:Sex Chromosomes; D019849:Sex Determination Processes; D012744:Sex Ratio
keywords: 
  Tigriopus californicus
  ; alternating selection; copepod; environmental sex determination; genetic sex determination; individual-based model; polygenic sex determination; sex ratio