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Evolutionary, molecular and comparative zoology
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RESEARCH ARTICLE
Contents Vol 55(6)

Evaluating molecular and behavioural sexing methods for the Australasian gannet (Morus serrator)

Claire Daniel A , Craig D. Millar A , Stefanie M. H. Ismar A , Brent M. Stephenson B and Mark E. Hauber A C
+ Author Affiliations
- Author Affiliations

A School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland 1143, New Zealand.

B Eco-Vista: Photography and Research, PO Box 8291, Havelock North 4157, New Zealand.

C Corresponding author. Email: m.hauber@auckland.ac.nz

Australian Journal of Zoology 55(6) 377-382 https://doi.org/10.1071/ZO07073
Submitted: 27 December 2007  Accepted: 22 May 2008   Published: 13 June 2007

Abstract

The availability of molecular methods for avian sex identification has revolutionised the study of sexual differences in behaviour, morphology, life-history traits and conservation management. We implemented the recommendations of a recent review of DNA-based sex-identification by (1) verifying the sex-specificity and (2) estimating the accuracy of different sex-assignment methods in an apparently monomorphic seabird, the Australasian gannet (Morus serrator). The polymerase chain reaction (PCR) method based on the amplification of the sex-linked chromodomain-helicase-DNA binding gene (CHD) repeatedly assigned the same sex in 96% (n = 27 replicates) and correctly sexed all individuals with known gonadal anatomy (n = 6). PCR and sex-specific restriction fragment length polymorphism (RFLPs) showed agreement for 99.5% of individuals (n = 201). DNA-sexed pairs known to be social mates consisted of a male and a female in 96% of pairs sexed by PCR (n = 77) and 98% of pairs sexed by RFLP (n = 65). DNA-sexed females were in the bottom and males in the top copulatory position in 86% of observed copulations (n = 43 individuals). These results validate assumptions that both membership in social pairs and different copulatory positions can serve as reliable behavioural proxies for field-based sex identification in this colonial and obligately biparental seabird.


Acknowledgements

We are grateful to the Department of Conservation Gisborne and Napier offices’ staff, veterinarians A. King (Massey University, Palmerston North) and B. Lenting (Lynfield and Hillsborough Veterinary Clinic), G. Ballard, R. Constantine, B. Gill (Auckland Museum), L Huynen (Allan Wilson Centre for Molecular Evolution, Massey University, Albany), A. Bunce, D. Dearborn, A. Gager, T. Landers, J. Matthews, E. Minot, D. Raubenheimer, S. Patel, G. Singh, T. Ward-Smith, local landowners, farm managers, the editor and referees of this journal, and many others for assistance, logistics, protocols, and discussions. This study was funded by the University of Auckland Research Committee and the Faculty of Science Research Development Fund to MEH and CDM and an Education New Zealand International Doctoral Scholarship to SI.


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