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The Evolution of Parental Care$
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Nick J. Royle, Per T. Smiseth, and Mathias Kölliker

Print publication date: 2012

Print ISBN-13: 9780199692576

Published to Oxford Scholarship Online: December 2013

DOI: 10.1093/acprof:oso/9780199692576.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 17 October 2021

Sex differences in parental care

Sex differences in parental care

(p.101) Chapter 6 Sex differences in parental care
The Evolution of Parental Care

Hanna Kokko

Michael D. Jennions

Oxford University Press

Sex differences in parental care are ubiquitous: biparental care is relatively rare in nature, and even then, the sexes often differ in the amount of care each provides. Although females do not always care more than males, such a bias exists in many taxa. This chapter reviews the reasons behind this female bias and considers explanations for exceptions. Anisogamy (eggs are larger than sperm) is the simplest possible, and oldest, form of parental care difference. The force that keeps sperm small is conceptually similar to the reason why males often provide little care once a zygote has formed. In both cases, there is a nonzero probability that investment might be wasted: a sperm might not fuse with an egg to form a zygote; and a zygote that is near a male might not carry his genes. The latter paternity problem arises due to sperm competition, which again is a result of anisogamy. Sperm, being smaller than eggs, tend to be the more abundant gametes, so that males, more often than females, find themselves in situations where they are uncertain about parentage to putative offspring. These factors tend to select against male care. Theory has recently made progress in understanding the exceptions to these general tendencies. Numerical asymmetries in the numbers of males and females, and the resultant sexual selection on each sex, can help to predict conditions where it is better to stay with current young (despite potential uncertainty about parentage) than to desert to seek new mating opportunities.

Keywords:   biparental care, anisogamy, male care, sexual selection, parentage, paternity, sperm competition, parental care

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