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RESEARCH ARTICLE
Contents Vol 20(2)

Generation of sex ratio biases in the red-tailed phascogale (Phascogale calura)

W. K. Foster A B D and D. A. Taggart A B C
+ Author Affiliations
- Author Affiliations

A School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia.

B Zoos South Australia, Frome Road, Adelaide, SA 5000, Australia.

C School of Medical Sciences, University of Adelaide, Adelaide, SA 5005, Australia.

D Corresponding author. Email: wendy.foster@adelaide.edu.au

Reproduction, Fertility and Development 20(2) 275-280 https://doi.org/10.1071/RD07031
Submitted: 15 February 2007  Accepted: 12 November 2007   Published: 4 January 2008

Abstract

Male semelparous dasyurid species are annual breeders that use a promiscuous mating system. These species have shown biases in litter sex ratios and, with females producing more young than they have available teats, this provides an opportunity for the manipulation of the sex ratio at birth. The sex ratio of embryos and pouch young, and the degree of embryonic overproduction, in red-tailed phascogales (Phascogale calura) was investigated to gain an understanding of the mechanism by which sex biases may be generated. The sex ratio of embryos did not differ from parity, but a male bias was observed in young attaching to teats. Females produced an average of 15.1 ± 1.9 corpora lutea and 10.5 ± 3.5 viable embryos, with no difference in fecundity observed with female age or weight. Because females only have eight teats, the overproduction of young, and male-biased attachment, was sufficient to explain the observed male bias in pouch young. No relationship was observed between maternal weight and sex ratio, but heavier females did tend to produce more ova. Meta-analysis of studies providing information on litter sex ratios in male semelparous dasyurid species did not show any consistent trend.

Additional keywords: dasyurid, fecundity, marsupial, reproductive investment.


Acknowledgements

The authors thank Adelaide Zoo for their assistance with animal housing, maintenance and project funding and Alice Springs Desert Park for supplying the animals. The authors also thank Natasha Sankovic and Monica Ruibal for providing primer sequences for the sexing of young and Lisa Miller and Tom Sullivan from the Public Health Department, University of Adelaide, for their assistance with the meta-analysis. Funding was obtained from the Royal Zoological Society of South Australia, the Schultz Foundation and a post-graduate scholarship from the University of Adelaide.


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