Costs of rearing the wrong sex: cross-fostering to manipulate offspring sex in tammar wallabies

Schwanz, Lisa E., and Robert, Kylie A. (2016) Costs of rearing the wrong sex: cross-fostering to manipulate offspring sex in tammar wallabies. PLoS ONE, 11 (2). pp. 1-14.

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Sex allocation theory assumes that offspring sex (son vs. daughter) has consequences for maternal fitness. The most compelling experiment to test this theory would involve manipulating offspring sex and measuring the fitness consequences of having the "wrong" sex. Unfortunately, the logistical challenges of such an experiment limit its application. In tammar wallabies (Macropus eugenii), previous evidence suggests that mothers in good body condition are more likely to produce sons compared to mothers in poor condition, in support of the Trivers-Willard Hypothesis (TW) of condition-dependent sex allocation. More recently, we have found in our population of tammar wallabies that females with seemingly poor access to resources (based on condition loss over the dry summer) are more likely to produce sons, consistent with predictions from the Local Resource Competition (LRC) hypothesis, which proposes that production of sons or daughters is driven by the level of potential competition between mothers and philopatric daughters. We conducted a cross-fostering experiment in free-ranging tammar wallabies to disassociate the effects of rearing and birthing offspring of each sex. This allowed us to test the prediction of the LRC hypothesis that rearing daughters reduces the future direct fitness of mothers post-weaning and the prediction of the TW hypothesis that rearing sons requires more energy during lactation. Overall, we found limited costs to the mother of rearing the "wrong" sex, with switching of offspring sex only reducing the likelihood of a mother having a pouch young the following year. Thus, we found some support for both hypotheses in that rearing an unexpected son or an unexpected daughter both lead to reduced future maternal fitness. The study suggests that there may be context-specific costs associated with rearing the "wrong" sex.

Item ID: 49349
Item Type: Article (Research - C1)
ISSN: 1932-6203
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© 2016 Schwanz, Robert. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funders: National Science Foundation (NSF), University of Western Australia (UWA), Australian Department of Defence
Projects and Grants: NSF IRFP 0754299, UWA Postdoctoral Research Fellowship, UWA Research Grants Scheme
Date Deposited: 12 Jun 2017 05:00
FoR Codes: 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310408 Life histories @ 50%
31 BIOLOGICAL SCIENCES > 3109 Zoology > 310901 Animal behaviour @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 100%
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