Research ArticleEVOLUTIONARY BIOLOGY

Darwinian sex roles confirmed across the animal kingdom

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Science Advances  12 Feb 2016:
Vol. 2, no. 2, e1500983
DOI: 10.1126/sciadv.1500983
  • Fig. 1 Sex-biased sexual selection across the animal kingdom.

    (A to C) Forest plots showing estimates of the sex bias in (A) the opportunity for selection (ΔI), (B) the opportunity for sexual selection (ΔIs), and (C) the Bateman gradient (Δβss). Effect sizes (lnCVR and Hedges’ d; see Materials and Methods) are shown with their 95% confidence intervals (CIs). Positive values indicate male-biased sexual selection parameters. Studies are grouped according to taxonomic ranks (color shades and icons).

  • Fig. 2 Sex-biased sexual selection and its evolutionary link to parental care and sexual dimorphism.

    (A to C) Frequency distributions and global mean effect sizes (filled squares) for sex differences in (A) the opportunity for selection (ΔI), (B) the opportunity for sexual selection (ΔIs), and (C) the Bateman gradient (Δβss). (D to I) Illustration of how sex differences in Bateman’s parameters covary with (D to F) parental care and (G to I) sexual dimorphism, respectively. Error bars are 95% CIs. Different lowercase letters indicate significant differences after stepwise Bonferroni correction at α = 0.05.

  • Fig. 3 The sex-role syndrome.

    Schematic illustration of conventional sex roles summarizing the three main findings of this study: (1) Sexual selection is stronger in males than in females, which must, by definition, be rooted in anisogamy. Stronger sexual selection on males translates in (2) female-biased parental care and (3) male-biased elaboration of traits. Arrowheads indicate direction of causality on the basis of current theory.

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/2/e1500983/DC1

    Fig. S1. PRISMA diagram depicting the data flow through the different phases of the meta-analysis.

    Fig. S2. Bivariate correlations of the effect sizes for sex differences in the three Bateman metrics, showing (A) ΔI versus ΔIs, (B) ΔI versus Δβss, and (C) ΔIs versus Δβss.

    Fig. S3. Comparison of (A) ΔI, (B) ΔIs, and (C) Δβss between higher-order taxa [taxa with K < 5 excluded: platyhelminthes (K = 1), molluscs (K = 4), and echinoderms (K = 2)].

    Fig. S4. Phylogenetic tree of all species included in the meta-analysis.

    Fig. S5. Funnel plots for (A to C) ΔI, (D to F) ΔIs, and (G to I) Δβss.

    Table S1. List of all primary studies included in the meta-analysis.

    References (81222)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. PRISMA diagram depicting the data flow through the different phases of the meta-analysis.
    • Fig. S2. Bivariate correlations of the effect sizes for sex differences in the three Bateman metrics, showing (A) ΔI versus ΔIs, (B) ΔI versus Δβss, and (C) ΔIs versus Δβss.
    • Fig. S3. Comparison of (A) ΔI, (B) ΔIs, and (C) Δβss between higher-order taxa taxa with K < 5 excluded: platyhelminthes (K = 1), molluscs (K = 4), and echinoderms (K = 2).
    • Fig. S4. Phylogenetic tree of all species included in the meta-analysis.
    • Fig. S5. Funnel plots for (A to C) ΔI, (D to F) ΔIs, and (G to I) Δβss.
    • Table S1. List of all primary studies included in the meta-analysis.
    • References (81–222)

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