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Extrapair mating between relatives in the barn swallow: a role for kin selection?
Oddmund Kleven1, Frode Jacobsen, Raleigh J Robertson
1University of Oslo Natural History Museum, Department of Zoology P.O. Box 1172 Blindern, NO-0318 Oslo, Norway. oddmund.kleven@nhm.uio.no
Biology Letters
|December 7, 2006
Summary
Female barn swallows engage in extrapair mating, but not to avoid inbreeding. Instead, they preferentially mate with related males, suggesting kin selection may drive this behavior.
Area of Science:
- Evolutionary biology
- Behavioral ecology
- Animal mating systems
Background:
- Female promiscuity is common in many species.
- The inbreeding avoidance hypothesis suggests females mate multiply to reduce genetic similarity with partners.
- This hypothesis predicts females should choose less related extrapair mates.
Purpose of the Study:
- To investigate the relatedness patterns in mating partners and parent-offspring relationships in the North American barn swallow (Hirundo rustica erythrogaster).
- To test the inbreeding avoidance hypothesis against observed mating behaviors.
- To explore alternative explanations for female extrapair mating.
Main Methods:
- Analysis of paternity and genetic relatedness among social and extrapair mating partners.
- Assessment of relatedness between parents and their within-pair and extrapair offspring.
- Utilizing the socially monogamous North American barn swallow as a model system.
Main Results:
- Extrapair mating partners were found to be more related than expected by random chance.
- Extrapair partners tended to be more related than social (within-pair) partners.
- Genetic parents showed higher relatedness to their extrapair young compared to their within-pair young.
Conclusions:
- The findings contradict the inbreeding avoidance hypothesis for female extrapair mating.
- A novel hypothesis, based on kin selection theory, is proposed to explain the observed mating patterns.
- Extrapair mating in barn swallows may serve to increase inclusive fitness through relatedness to offspring and their kin.
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