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Title: Extra-pair reproduction : variation and indirect fitness consequences in song sparrows, Melospiza melodia
Author: Sardell, Rebecca
ISNI:       0000 0004 2717 4983
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2011
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Simultaneous polyandry is common in a wide range of taxa including socially monogamous species. Despite considerable research effort, the forces driving the evolution of extra-pair reproduction remain uncertain, requiring direct and indirect selection on males and females to be quantified. One primary prediction of the hypothesis that there is positive indirect selection on female extra-pair reproduction is that extra-pair young (EPY) sired by extra-pair males will be fitter than within-pair young (WPY) sired by the female’s social mate. Robust testing of this prediction requires data on lifetime fitness with at least two generations corrected for extra-pair paternity (EPP). In the present study I used molecular genetics and Bayesian full probability models to assign sires to >99% of 2343 offspring over 17 cohorts from a population of wild song sparrows, Melospiza melodia, with high individual-level confidence. Using these data I tested the key prediction that EPY will have higher fitness than their WPY maternal half-siblings, measuring fitness as survival to major life-history stages and lifetime reproductive success. Contrary to widespread prediction, EPY tended to have lower fitness than their WPY maternal half-siblings across virtually all measures of fitness. I also found evidence for sex-specific relative fitness of EPY and WPY and that the offspring of EPY and WPY differ in their own fitness suggesting that there may be both sex-specific and inter-generational effects of extra-pair status. Overall, my results suggested that there is not positive indirect selection on female extra-pair reproduction, and if anything, there may be weak negative indirect selection against female extra-pair reproduction. Finally, I used the comprehensive long-term dataset on EPP to explore individual and population-level correlates of variation in EPP rate and discussed the implications of these findings for our understanding of the evolution of extra-pair reproduction.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available