Females may choose mates based on the expression of secondary sexual characters that signal direct, material fitness benefits or indirect, genetic fitness benefits. Genetic benefits are acquired in the generation subsequent to that in which mate choice is performed, and the maintenance of genetic variation in viability has been considered a theoretical problem. Consequently, the magnitude of indirect benefits has traditionally been considered to be small. Direct fitness benefits can be maintained without consideration of mechanisms sustaining genetic variability, and they have thus been equated with the default benefits acquired by choosy females. There is, however, still debate as to whether or not males should honestly advertise direct benefits such as their willingness to invest in parental care. We use meta-analysis to estimate the magnitude of direct fitness benefits in terms of fertility, fecundity and two measures of paternal care (feeding rate in birds, hatching rate in male guarding ectotherms) based on an extensive literature survey. The mean coefficients of determination weighted by sample size were 6.3%, 2.3%, 1.3% and 23.6%, respectively. This compares to a mean weighted coefficient of determination of 1.5% for genetic viability benefits in studies of sexual selection. Thus, for several fitness components, direct benefits are only slightly more important than indirect ones arising from female choice. Hatching rate in male guarding ectotherms was by far the most important direct fitness component, explaining almost a quarter of the variance. Our analysis also shows that male sexual advertisements do not always reliably signal direct fitness benefits.
Pischedda A, Chippindale AK. Pischedda A, et al. Evolution. 2017 Jun;71(6):1710-1718. doi: 10.1111/evo.13240. Epub 2017 Apr 28. Evolution. 2017. PMID: 28369895
Slatyer RA, Mautz BS, Backwell PR, Jennions MD. Slatyer RA, et al. Biol Rev Camb Philos Soc. 2012 Feb;87(1):1-33. doi: 10.1111/j.1469-185X.2011.00182.x. Epub 2011 May 5. Biol Rev Camb Philos Soc. 2012. PMID: 21545390
Neff BD, Pitcher TE. Neff BD, et al. Mol Ecol. 2005 Jan;14(1):19-38. doi: 10.1111/j.1365-294X.2004.02395.x. Mol Ecol. 2005. PMID: 15643948
Radwan J. Radwan J. Genetica. 2008 Sep;134(1):113-27. doi: 10.1007/s10709-007-9203-0. Epub 2007 Sep 15. Genetica. 2008. PMID: 17874278 Review.
Booksmythe I, Mautz B, Davis J, Nakagawa S, Jennions MD. Booksmythe I, et al. Biol Rev Camb Philos Soc. 2017 Feb;92(1):108-134. doi: 10.1111/brv.12220. Epub 2015 Sep 25. Biol Rev Camb Philos Soc. 2017. PMID: 26405787 Review.
Fissette SD, Buchinger TJ, Tamrakar S, Scott AM, Li W. Fissette SD, et al. Behav Ecol. 2024 Feb 1;35(2):arae006. doi: 10.1093/beheco/arae006. eCollection 2024 Mar-Apr. Behav Ecol. 2024. PMID: 38379814 Free PMC article.
Hegyi G, Laczi M, Szabó G, Sarkadi F, Török J. Hegyi G, et al. Sci Rep. 2023 Oct 31;13(1):18770. doi: 10.1038/s41598-023-45348-0. Sci Rep. 2023. PMID: 37907494 Free PMC article.
Henshaw JM, Fromhage L, Jones AG. Henshaw JM, et al. Proc Natl Acad Sci U S A. 2022 Aug 16;119(33):e2206262119. doi: 10.1073/pnas.2206262119. Epub 2022 Aug 8. Proc Natl Acad Sci U S A. 2022. PMID: 35939704 Free PMC article.
Yang X, Berman CM, Hu H, Hou R, Huang K, Wang X, Zhao H, Wang C, Li B, Zhang P. Yang X, et al. Curr Zool. 2021 May 26;68(2):133-142. doi: 10.1093/cz/zoab044. eCollection 2022 Apr. Curr Zool. 2021. PMID: 35355945 Free PMC article.
Cronin AD, Smit JAH, Muñoz MI, Poirier A, Moran PA, Jerem P, Halfwerk W. Cronin AD, et al. Biol Rev Camb Philos Soc. 2022 Aug;97(4):1325-1345. doi: 10.1111/brv.12845. Epub 2022 Mar 9. Biol Rev Camb Philos Soc. 2022. PMID: 35262266 Free PMC article. Review.