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Title: Evolutionary ecology of sex change
Author: Allsop, David John
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2003
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In this thesis I investigate the evolutionary causes and consequences of the sex change life history strategy. I test a priori predictions regarding the social and ecological context in which selection favours sex change and/or the production of alternative mating strategies with a field study and laboratory experiment using populations of the marine teleost fish Coryphopterus personatus. The experimental data demonstrates that C. personatus retains the ability to facultatively switch its gender in response to local social conditions, but demographic field observations indicate that the fish may use this trait relatively little on atoll fringing reefs. I discuss these observations in the context of the distribution of essential ecological resources, the emergent mating system and the resulting impact of the mating system on selection for sex change. I examine the evolution of the sex ratio in sex changing organisms. I analyse sex ratio data for 121 species of sex changing animals using both standards cross species techniques and formal comparative method. The data supports the theories that (a) the sex ratio should be biased towards the first sex, and (b) the magnitude of the sex ratio bias should be more for protogynous species than for protandrous species. I found support amongst the vertebrates for the theory that the sex ratio has bias should be less extreme for species in which a proportion of the ‘second’ sex mature directly from juvenile phase (early maturers), but this support does not extend to the whole sex change phylogeny, although the reason my be a lack of appropriate data. I draw upon the statistical techniques of dimensionaless analysis in order to test the prediction that sex change should occur at the same relative age and body size for populations or species that share similar relationships between crucial life history parameters.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available