Date of Award


Degree Type


Degree Name

Master of Science




Dr. Elizabeth MacDougall-Shackleton


Understanding the evolutionary forces that maintain genetic diversity in natural populations is a major goal in behavioural and evolutionary ecology. I investigated the relationships between individual genetic diversity and pairwise genetic similarity (as measured by 17 microsatellite loci), mating strategies, parental investment, and overwinter survivorship, in song sparrows Melospiza melodia. Genetic similarity of socially mated pairs was not significantly different from random expectations, but females were more likely to produce extra-pair offspring when their social mate was genetically similar. Highly heterozygous males fed their nestlings significantly more often than did their less diverse counterparts, although this pattern was not observed in females. Interestingly, the high parental investment by genetically diverse males may come at a cost, as I discovered a highly significant negative relationship between male heterozygosity and overwinter survivorship. Collectively these findings suggest that trade-offs between current and future reproductive investment may temper the fitness advantages of genetic diversity.



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