Another set of responses and correlated responses to selection on age at reproduction in Drosophila melanogaster

Abstract

Ageing is the decline in survival probability and fertility later in adult life. It can evolve through mutation accumulation and pleiotropy. Artificial selection by age at reproduction is a useful method for detecting the effects of pleiotropy, and for producing lines that differ in their rate of ageing for further analysis. However, the approach has encountered difficulties from gene–environment interaction and inadvertent selection. We have produced a new set of selection lines in Drosophila melanogaster, breeding from either ‘young’ or ‘old’ adults, and avoiding some of the difficulties present in previous studies. Breeding from older adults resulted in an evolutionary increase in survival but, contrary to all previous studies using this method, in no increase in late–life fertility. The increase in survival was accompanied by an evolutionary decline in fertility early in adult life, confirming the importance of pleiotropy in the evolution of ageing. Contrary to previous studies, there were no correlated responses to selection in the pre–adult period; development time, larval competitive ability and adult size achieved did not differ between the lines from the two selection regimes.