Behavioral Ecology Advance Access originally published online on March 31, 2009
Behavioral Ecology 2009 20(3):575-584; doi:10.1093/beheco/arp034
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Why some species of birds do not avoid inbreeding: insights from New Zealand robins and saddlebacks
a Department of Zoology, University of Otago, P.O. Box 56, Dunedin, 9054, New Zealand b Department of Forest Sciences, Centre for Applied Conservation Research, 3041 - 2424 Main Mall, Vancouver, British Columbia, Canada V6T 1Z4 c Department of Biological and Environmental Science, P.O. Box 56, University of Helsinki, FIN-00014 Helsinki, Finland d School of Botany and Zoology, Banks Wing Building, Australian National University, Canberra ACT 0200, Australia e Wildlife Ecology Group, Institute of Natural Resources, P.O. Box 11 222, Massey University, Palmerston North, New Zealand
Address correspondence to I.G. Jamieson. E-mail: ian.jamieson{at}stonebow.otago.ac.nz.
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Abstract |
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When dispersal options are limited and encounters with relatives are likely, individuals need to recognize and avoid mating with kin to avoid the fitness costs of close inbreeding. New Zealand robins and saddlebacks are genetically monogamous and possess life-history traits that predict they should show zero tolerance of close inbreeding. However, of 11 population-years of pedigree data, there was evidence of inbreeding avoidance in only 1 year. We also found no indication that incestuous pairings were avoided or that individuals were choosing genetically dissimilar mates based on microsatellite DNA analysis. Furthermore, a review of the literature revealed that inbreeding avoidance via kin recognition is common in cooperatively breeding birds, but pair-breeding birds such as robins and saddlebacks mate randomly with respect to relatedness. A model that incorporates encounter rates with close kin for various degrees of mate-searching effort shows that inbreeding avoidance is beneficial at intermediate to high levels of encounter rates with close kin (as found in cooperative breeders), but that random mating is more beneficial at low or extremely high encounter rates. We conclude that random mating normally results in such low rates of close inbreeding that it exerts negligible selection pressure to evolve kin recognition. Consequently, many threatened species are unlikely to have a natural "built-in" mechanism for avoiding close inbreeding, and the assumption of random mating built into many population viability models may be appropriate.
Key words: genetic similarity, inbreeding avoidance, kin recognition, pedigrees, random mating.
Received 30 June 2008; revised 26 January 2009; accepted 16 February 2009.