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Title: An investigation of inbreeding depression and purging in captive populations
Author: Boakes, E. H.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2006
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I use simulated pedigree and fitness data to test the statistical power of a regression model proposed by Ballou (J. Heredity, 88, 169-178, 1997) to detect inbreeding depression and purging. Finding the model to be lacking in power when used to analyse typical zoo pedigrees, I develop an alternative, more powerful model. I use both of these models to investigate the effects of inbreeding in 136 zoo populations, encompassing 109 species of mammals, birds, reptiles and amphibians. A significant cross-population trend in inbreeding depression is detected, as is a cross-population trend of purging in those populations which showed negative effects of inbreeding. The average change in inbreeding depression due to purging is < 2%, however, suggesting that fitness benefits are rarely appreciable. The study re-emphasises the necessity to avoid inbreeding in captive breeding programs and shows that purging cannot be relied upon to remove deleterious alleles from zoo populations. The severity of inbreeding depression appears to vary among taxa but few predictors of a population’s response to inbreeding are found. The models are most likely to detect inbreeding depression in large populations, i.e. in populations in which their statistical power is maximised. By analysing founders’ contributions to inbreeding, I find that random founder effects play a part in determining whether a population suffers from inbreeding depression. I also show that inbreeding depression may have differing effects on sexes but find no evidence of a consistent sex-bias. Susceptibility to inbreeding depression may therefore depend on a complex interaction of genetic, environmental and stochastic factors.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available