Evolution of the life history in Drosophila melanogaster : a study of responses to artificial selection by age at breeding

• Main Author: Roper, Caroline
• Published: University of Edinburgh 1992
• Subjects: 591.35
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.661367

Trade-offs between early life reproductive success and subsequent survival and reproductive success are central to theoretical models of life history evolution. Such models demonstrate how trade-offs might influence the evolution of reproductive strategies and senescent decline. Quantitative genetic theory predicts that additive genetic variance for functionally related fitness traits should be negatively correlated (Falconer 1981). The research described here attempted to verify the existence of trade-offs by examining additive genetic covariance for life history traits in a laboratory adapted population of <i>Drosophila melanogaster</i> using artificial selection. In particular it looked for evidence of trade-offs involving reproductive costs in males, trade-offs between preadult development and senescence, and life history adaptations to density. Selection by age at breeding was applied to a laboratory adapted stock of <i>Drosophila melanogaster</i> to investigate additive genetic covariance for early life reproductive success and subsequent survival and reproductive success. Selection to breed either early or late in life was applied by propagating from either young or aged adult flies. Male selection responses were characterised using age specific measures of behaviour, competitive reproductive success and survival. Selected lines were compared with the original stock in order to deduce the direction of selection responses. Those selected to breed late in life were found to have evolved enhanced survival, increased lifetime reproductive output, and improved late life reproductive success. No evidence for a negative genetic correlation between these traits and early reproductive success was found. The possibility that they had evolved at a cost to preadult survival and growth rate was also investigated, but again no evidence for a trade-off was found. It was concluded that enhanced survival, increased lifetime reproductive output, and improved late life reproductive success had evolved by the elimination of deleterious age-specific mutations.