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Sex allocation, juvenile mortality, and the costs imposed by offspring on parents and siblings


Kahn, A T; Jennions, Michael D; Kokko, Hanna (2015). Sex allocation, juvenile mortality, and the costs imposed by offspring on parents and siblings. Journal of Evolutionary Biology, 28(2):428-437.

Abstract

Generally, sex-specific mortality is not expected to affect optimal patterns of sex allocation. Several authors have, however, made verbal arguments that this is not true if juvenile mortality is sex-specific during the period of parental care. Here, we provide formal mathematical models exploring the effect of such mortality on optimal sex allocation. We confirm the prediction that biased production of the sex with higher mortality during care is favoured. Crucially, however, this is only true when juvenile mortality in the period of parental care frees up resources for their current/future siblings (i.e. the saved investment is transferable). Furthermore, we show that while optimal sex allocation is consistent with the theory of equal investment (as asserted by previous authors), thinking in terms of equal investment is not readily feasible in some scenarios. We also show that differences in early mortality overcome biased sex allocation such that the sex ratio at independence is generally, but not always, biased in the opposite direction from that at birth. Our models should prove useful to empiricists investigating the effect of sex-specific juvenile mortality and antagonistic sibling interactions on sex allocation.

Abstract

Generally, sex-specific mortality is not expected to affect optimal patterns of sex allocation. Several authors have, however, made verbal arguments that this is not true if juvenile mortality is sex-specific during the period of parental care. Here, we provide formal mathematical models exploring the effect of such mortality on optimal sex allocation. We confirm the prediction that biased production of the sex with higher mortality during care is favoured. Crucially, however, this is only true when juvenile mortality in the period of parental care frees up resources for their current/future siblings (i.e. the saved investment is transferable). Furthermore, we show that while optimal sex allocation is consistent with the theory of equal investment (as asserted by previous authors), thinking in terms of equal investment is not readily feasible in some scenarios. We also show that differences in early mortality overcome biased sex allocation such that the sex ratio at independence is generally, but not always, biased in the opposite direction from that at birth. Our models should prove useful to empiricists investigating the effect of sex-specific juvenile mortality and antagonistic sibling interactions on sex allocation.

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2 citations in Web of Science®
1 citation in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:competition; reproductive costs; sex-ratio; sexual conflict; sexual selection
Language:English
Date:2015
Deposited On:20 Feb 2015 13:48
Last Modified:05 Apr 2016 18:49
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:1010-061X
Additional Information:This is the accepted version of the following article: Kahn, A. T., Jennions, M. D. and Kokko, H. (2015), Sex allocation, juvenile mortality and the costs imposed by offspring on parents and siblings. Journal of Evolutionary Biology. doi: 10.1111/jeb.12578, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/jeb.12578/abstract.
Publisher DOI:https://doi.org/10.1111/jeb.12578
PubMed ID:25546092

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