title: The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos.
abstract: Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates.
authors.affiliation: Universidad de Vigo, Vigo 36310, Spain.
authors.forename: P
authors.identifier: 0000-0002-3644-8507
authors.initials: P
authors.lastname: Morán
authors.affiliation: IFREMER-INRA, BP 117, 29450 Sizun, France.
authors.forename: L
authors.initials: L
authors.lastname: Labbé
authors.affiliation: BioSciences, CSAR, Swansea University, Swansea SA2 8PP, UK c.garciadeleaniz@swansea.ac.uk.
authors.forename: C
authors.identifier: 0000-0003-1650-2729
authors.initials: C
authors.lastname: Garcia de Leaniz
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000502:physiology; D005260:Female; D008297:Male; D009026:Mortality; D012744:Sex Ratio; D014337:Trout / Q000196:embryology* / Q000235:genetics*
keywords: embryo development; genetic conflict; genetic incompatibility; sex determination; sex ratio; sex-specific mortality