Reverse sex-biased philopatry in a cooperative bird: genetic consequences and a social cause

Authors

  • E. C. BERG,

    1. Department of Biology, Portland State University, Box 751, Portland, OR 97207-0751, USA
    2. Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616, USA
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  • J. M. EADIE,

    1. Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616, USA
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  • T. A. LANGEN,

    1. Departments of Biology and Psychology, Clarkson University, Box 5805 Potsdam, NY 13699-5805, USA
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  • A. F. RUSSELL

    1. Department of Animal & Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
    2. Centre for the Integrative Study of Animal Behaviour, Macquarie University, Sydney, NSW 2109, Australia
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  • Elena Berg is a postdoctoral researcher at Portland State University in Portland, Oregon, and a senior research fellow at UCLA's Center for Tropical Research. Her research interests lie in the ecology and evolution of cooperative behaviour in group-living birds, as well as in how behaviour, morphology, and genetic structure vary across different environments and spatial scales. John Eadie is a professor in wildlife ecology at the University of California, Davis. His research and teaching interests are in behavioural ecology, population biology and molecular ecology. His current work focuses on exploring the linkages among behaviour, genetic structure, and population dynamics in birds, especially waterfowl, with particular consideration to management and conservation applications. Tom Langen is a professor in biology and psychology at Clarkson University, New York. His research interests focus on social development, cognition, and foraging behaviour. He also is working on applied research projects related to the impact of roads and human land-use practices on animal behaviour and the environment. Andrew Russell is a Royal Society Research Fellow at the University of Sheffield, UK and a visiting scholar at Macquarie University, Sydney, Australia. His research focuses on maternal allocation and differential allocation in cooperative birds and mammals, the evolution of cooperative breeding in birds and mammals, and individual contributions to cooperation in vertebrates.

Elena C. Berg, Fax: +1 (503) 725-3888; E-mail: ecberg@pdx.edu

Abstract

The genetic structure of a group or population of organisms can profoundly influence the potential for inbreeding and, through this, can affect both dispersal strategies and mating systems. We used estimates of genetic relatedness as well as likelihood-based methods to reconstruct social group composition and examine sex biases in dispersal in a Costa Rican population of white-throated magpie-jays (Calocitta formosa, Swainson 1827), one of the few birds suggested to have female-biased natal philopatry. We found that females within groups were more closely related than males, which is consistent with observational data indicating that males disperse upon maturity, whereas females tend to remain in their natal territories and act as helpers. In addition, males were generally unrelated to one another within groups, suggesting that males do not disperse with or towards relatives. Finally, within social groups, female helpers were less related to male than female breeders, suggesting greater male turnover within groups. This last result indicates that within the natal group, female offspring have more opportunities than males to mate with nonrelatives, which might help to explain the unusual pattern of female-biased philopatry and male-biased dispersal in this system. We suggest that the novel approach adopted here is likely to be particularly useful for short-term studies or those conducted on rare or difficult-to-observe species, as it allows one to establish general patterns of philopatry and genetic structure without the need for long-term monitoring of identifiable individuals.

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