The effect of sex ratio on male reproductive success in painted turtles, Chrysemys picta

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The effect of sex ratio on male reproductive success in painted turtles, Chrysemys picta

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dc.contributor.advisor Brooks, Ronald J.
dc.contributor.advisor Fu, Jinzhong
dc.contributor.author Hughes, Elinor Jane
dc.date 2010-08-19
dc.date.accessioned 2011-08-25T21:04:26Z
dc.date.available 2011-08-25T21:04:26Z
dc.date.issued 2011-08-25
dc.identifier.uri http://hdl.handle.net/10214/2871
dc.description.abstract Sex ratio theory suggests that the strength of intersexual selection will increase as a population more male-biased; reflecting increased selectivity in mate choice. Populations of pond turtle have varying adult sex ratios, in painted turtles (Chrysemys picta), reported sex ratios range from female biased (1:3) to male biased (3:1). I investigated the effect of sex ratio on male reproductive success (quantified as “fertilization success”) in painted turtles. I examined the mating system of painted turtles in a female-biased population using microsatellite paternity analysis, relating variation in male fertilization success to male phenotype and offspring survival, employed ex situ behavioural observation to clarify the mechanism behind the variation in male fertilization success and used agent-based modeling to simulate the effects of changing sex ratio, population density and proportions of male phenotype on male fertilization success. Small males contributed sperm to a greater number of clutches than did larger males, but were not more likely to reproduce in a season than larger males. There was no offspring fitness advantage related to male body size and no relationship between male claw length and fertilization success. Large male painted turtles courted at a higher frequency than small males. I found no relationship between male courtship behavior and claw length. Females showed no preference for males of any phenotype. Agent-based simulations were based on the distribution of best fit from the observed data; an amalgam of two Poisson distributions, each with its own probability of success and proportional representation in the final distribution. Increased female sex ratio bias, increased population density and increased proportions of “more successful” males all increased the mean and variance of male fertilization success, based on increased encounter rate among turtles. Small and large male painted turtles enjoy different fertilization success. It is uncertain whether this difference is based on active female choice, cryptic female choice, sperm competition or a combination of factors. Sex ratio simulations predict the opposite result as that predicted by sex ratio theory. These contrary results should be compared to simulations manipulating choosiness and field data from painted turtle populations to clarify mechanisms influencing male reproductive success. en_US
dc.language.iso en en_US
dc.subject painted turtle en_US
dc.subject Chrysemys picta en_US
dc.subject sex ratio en_US
dc.subject male reproductive success en_US
dc.subject sexual selection en_US
dc.subject mate choice en_US
dc.subject agent based model en_US
dc.subject paternity en_US
dc.subject microsatellite en_US
dc.title The effect of sex ratio on male reproductive success in painted turtles, Chrysemys picta en_US
dc.type Thesis en_US
dc.degree.programme Integrative Biology en_US
dc.degree.name Doctor of Philosophy en_US
dc.degree.department Department of Integrative Biology en_US


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