The Journal of Heredity 1992:83(5):350-355
© 1992 The American Genetic Association 83:350-355
research-article |
Sex-Specific Restriction Fragments and Sex Ratios Revealed by DNA Fingerprinting in the Brown Skua
School of Biological Sciences of the University of Auckland New Zealand
Address reprint requests to Craig Millar, Evolutionary Genetics Laboratory, Department of Zoology, University of Auckland, Private Bag, Auckland, New Zealand.
Abstract
DNA fingerprinting was used to assign the sex of individuals of brown skua (Catharacta lonnbergi). A population of this sexually monomorphic sea bird is found on the Chatham Islands off the coast of New Zealand. A large proportion of the individuals within this population breed communally. Hybridization of the DNA fingerprinting probe pV472 to genomic DNA from brown skua revealed several high molecular weight DNA fragments present exclusively in females. This finding is consistent with the assignment of sex based on the available morphometric and behavioral data. We conclude that these restriction fragments are located on the W chromosome. Consequently, the presence of these fragments can be used to identify female adults and chicks. We recorded a biased sex ratio among adult birds in breeding territories, with almost twice as many males as females. In contrast, the sex ratio among chicks approximates 1:1. These results are discussed in relation to contemporary ideas about the evolution of communal breeding.