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Title: The evolution of life histories in Drosophila melanogaster : costs of reproduction and the responses to artificial selection on age at reproduction
Author: Prowse, Nicholas Brian
ISNI:       0000 0001 3502 4780
Awarding Body: University of London
Current Institution: University College London (University of London)
Date of Award: 1997
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The demographic and physiological effects of reproduction on male survivorship and fertility in Drosophila melanogaster were examined by manipulating reproductive status part way through life. Reproductive costs can take the form of either an instantaneous elevation of risk or an irreversible decline in fitness, and the relative importance of these was considered. The impact of variation in individual fitness was also investigated. Early reproduction permanently damaged both survival and fecundity, with the cost to fertility being the greater of the two. Sterility appeared attributable to a reduced sperm count. Risk played an apparently minor role. Analyses of survival rates using the Gompertz parameters gave a misleading measure of ageing, which should also include the impact on fertility. Potential indicators of individual frailty were used to assess the effect of cohort heterogeneity on the interpretation of reversal experiments. The impact of such variation on survival and fertility was negligible. Two established selection regimes, selected for early and late life fitness under controlled density conditions in the absence of inadvertant selection, were examined for correlated responses to selection. Two hypotheses were tested. The first, that selection on age at reproduction would cause a divergence in adult body size and dry weight, larval viability and pre-adult development time, was disproved. The second hypothesis was that selection would result in reduced reproductive investment in favour of survival, and a trade off between survival and early fecundity was found in both sexes to support this. Apart from early life fecundity, no evidence was found for the evolution of female reproductive biology under selection. Comparisons were made with reference to the original base stock. The significance of the observed selection responses in the context of the evolution of senescence was discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Zoology