Consequences of sex change for effective population size

Waples, RS; Mariani, S; Benvenuto, C

Abstract

Sequential hermaphroditism, where males change to females (protandry) or the reverse (protogyny), is widespread in animals and plants and can be an Evolutionarily Stable Strategy (ESS) if fecundity rises faster with age in the second sex. Sequential hermaphrodites also generally have sex ratios skewed toward the initial sex, and standard theory based on fixed sexes indicates that this should reduce effective population size (Ne) and increase deleterious effects of genetic drift. We show that despite having skewed sex ratios, populations that change sex at the ESS age do not have reduced Ne compared to fixed-sex populations with an even sex ratio. This implies that the ability of individuals to operate as both male and female allows the population to avoid some evolutionary constraints imposed by fixed sexes. Furthermore, Ne would be maximized if sex change occurred at a different (generally earlier) age than is selected for at the individual level, which suggests a potential conflict between individual and group selection. We also develop a novel method to quantify the strength of selection for sex reversal.

Citation

Waples, R., Mariani, S., & Benvenuto, C. (2018). Consequences of sex change for effective population size. Proceedings of the Royal Society B: Biological Sciences, 285(1893), 20181702. https://doi.org/10.1098/rspb.2018.1702

• Journal Article Type: Article
• Acceptance Date: Nov 12, 2018
• Online Publication Date: Dec 12, 2018
• Publication Date: Dec 19, 2018
• Deposit Date: Nov 19, 2018
• Publicly Available Date: Nov 19, 2018
• Journal: Proceedings of the Royal Society B
• Print ISSN: 0962-8452
• Electronic ISSN: 1471-2954
• Publisher: The Royal Society
• Volume: 285
• Issue: 1893
• Pages: 20181702
• DOI: https://doi.org/10.1098/rspb.2018.1702
• Publisher URL: https://doi.org/10.1098/rspb.2018.1702
• Related Public URLs: http://rspb.royalsocietypublishing.org/
• Additional Information: Funders : Science Foundation Ireland;Irish Research Council