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A genetic analysis of the mating system of sockeye salmon Mahranvar, Ladan


It has now been widely shown that the genetic mating system of an organism determined using genetic markers can be very different to the social mating system based on behavioural observations. However, it is less well known what particular characteristics make an individual more or less successful than expected from the observed system. I present the first attempt to measure individual genetic reproductive success, as evidenced by microsatellite parentage assignment, and to compare this measure to the behavioural mating success in sockeye salmon, Oncorhynchus nerka. Approximately 40% of the variation in the genetic reproductive success of males was accounted for by the behavioural estimates of dominance and consort behaviour, whereas no reasonable behavioural estimate of female genetic success, measured as her genetic mate quality, was found. There was a high variance in individual reproductive success in males, and a high number of mates acquired by both males and females, suggesting that multiple mating partners is a rule rather than an exception. There was also a significant correlation between the number of genetic mates acquired and the number of offspring sired in males. This study also investigated whether any traits (size, shape, energy content, longevity) predicted the social mating success of males and females. I found little evidence supporting the prediction from previous studies of a significant correlation between individual size and social mating success for either males or females. Instead, body shape (exaggeration of secondary sexual characteristics) and longevity predicted dominance and consort behaviour in male sockeye salmon, and pre-spawning energy content predicted female longevity and social mating success. Finally, I present path models for both males and females describing the causal relationships among life history traits, social mating success and genetic reproductive success (or genetic mate quality in females) based on my previous results. Overall, these results indicate that this species' mating system is more flexible than previously thought and suggest that the behavioural estimates of mating success are not always successful predictors of the genetic reproductive success. Whether this low congruence is due to a high sneaking rate or to poor estimates of behavioural or genetic spawning success is unknown.

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