Heterozygosity and fitness benefits of extra-pair mate choice in the White-rumped Swallows

FERRETTI, VALENTINA; MASSONI, VIVIANA; BULIT, FLORENCIA; WINKLER, D. W.; IRBY J. LOVETTE

BEHAVIORAL ECOLOGY

OXFORD UNIV PRESS INC

Lugar: Oxford; Año: 2011

1045-2249

There is growing evidence that females that engage in extra-pair matings choose males with whom they are more genetically compatible, increasing their offspring’s fitness through increased heterozygosity. We looked at fitness benefits of extra-pair matings and tested the heterozygosity hypothesis in White-rumped Swallows (Tachycineta leucorrhoa) breeding in Argentina using a panel of 12 highly variable microsatellite loci. We found that broods with extra-pair offspring fledged more young than broods with no extra-pair offspring. Extra-pair offspring had a higher probability of surviving than within-pair offspring, but these two groups did not differ in their level of heterozygosity. Overall, young that died were more heterozygous than the ones that fledged. Neither the heterozygosity of the female nor her social mate, nor the genetic similarity of the social pair, predicted the presence of extra-pair young. Instead, females chose extra-pair mates that were more genetically similar to themselves. Our results do not support the heterozygosity hypothesis, suggesting that other mechanisms should be considered to explain the adaptive function of female choice for extra-pair mates.