Abstract
The local-resource-competition hypothesis predicts that where philopatric offspring compete for resources with their mothers, offspring sex ratios will be biased in favour of the dispersing sex. This should produce variation in sex ratios between populations in relation to differences in the availability of resources for philopatric offspring. However, previous tests of local resource competition in mammals have used indirect measures of resource availability and have focused on sex-ratio variation between species or individuals rather than between local populations. Here, we show that the availability of den sites predicts the offspring sex ratio in populations of the common brushtail possum. Female possums defend access to dens, and daughters, but not sons, occupy dens within their mother's range. However, the abundances of possums in our study areas were determined principally by food availability. Consequently, in food-rich areas with a high population density, the per-capita availability of dens was low, and the cost of having a daughter should have been high. This cost was positively correlated with male bias in the sex ratio at birth. Low per capita availability of dens was correlated with male bias in the sex ratio at birth.
Full Text
The Full Text of this article is available as a PDF (119.0 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Clutton-Brock T. H., Iason G. R. Sex ratio variation in mammals. Q Rev Biol. 1986 Sep;61(3):339–374. doi: 10.1086/415033. [DOI] [PubMed] [Google Scholar]
- Computer software for performing likelihood tests of pedigree relationship using genetic markers. Mol Ecol. 1999 Jul;8(7):1231–1234. doi: 10.1046/j.1365-294x.1999.00664.x. [DOI] [PubMed] [Google Scholar]
- Davison M. J., Ward S. J. Prenatal bias in sex ratios in a marsupial, Antechinus agilis. Proc Biol Sci. 1998 Nov 7;265(1410):2095–2099. doi: 10.1098/rspb.1998.0545. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Drickamer L. C. Pregnancy in female house mice exposed to urinary chemosignals from other females. J Reprod Fertil. 1999 Mar;115(2):233–241. doi: 10.1530/jrf.0.1150233. [DOI] [PubMed] [Google Scholar]
- Johnson C. N. Dispersal and the sex ratio at birth in primates. Nature. 1988 Apr 21;332(6166):726–728. doi: 10.1038/332726a0. [DOI] [PubMed] [Google Scholar]
- Marshall T. C., Slate J., Kruuk L. E., Pemberton J. M. Statistical confidence for likelihood-based paternity inference in natural populations. Mol Ecol. 1998 May;7(5):639–655. doi: 10.1046/j.1365-294x.1998.00374.x. [DOI] [PubMed] [Google Scholar]
- Packer C., Collins D. A., Eberly L. E. Problems with primate sex ratios. Philos Trans R Soc Lond B Biol Sci. 2000 Nov 29;355(1403):1627–1635. doi: 10.1098/rstb.2000.0725. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Taylor A. C., Cooper D. W. Microsatellite markers for the phalangerid marsupial, the common brushtail possum (Trichosurus vulpecula). Mol Ecol. 1998 Dec;7(12):1780–1782. doi: 10.1046/j.1365-294x.1998.00517.x. [DOI] [PubMed] [Google Scholar]