Evolution of increased early-life fecundity but faster reproductive senescence in Drosophila melanogaster females through adaptation to chronic live-yeast deprivation

Abstract

Reproductive output is often constrained by availability of macronutrients, especially protein. Long term protein restriction, therefore, is expected to select for traits that maximize reproductive output in spite of such nutritional challenge. We subjected four replicate populations of Drosophila melanogaster to a complete deprivation of live-yeast supplement, thereby mimicking a protein restricted ecology. As yeast supplement is a key source of protein, such an ecology is expected to strongly limit reproductive output, especially in females. Following 24 generations of experimental evolution, compared to their matched controls, females from experimentally evolved populations showed increase in reproductive output early in life, both in presence and absence of yeast supplement. The observed increase in reproductive output was not associated with any accommodating alteration in egg size; and development time, pre-adult survivorship, and body mass at eclosion of the progeny. There was no evidence for evolution of lifespan and lifelong cumulative reproductive output in females. However, females from experiment regime were found to have a significantly faster rate of reproductive senescence, as indicated by a faster rate of age related decline in reproductive output following the attainment of the reproductive peak. Therefore, adaptation to yeast deprivation ecology in our study involved a novel reproductive strategy whereby females attained higher reproductive output early in life followed by faster reproductive aging. To the best of our knowledge, this set of results is one of the most clear demonstration of optimization of fitness by fine tuning of reproductive schedule during adaptation to a prolonged nutritional deprivation. Supplementary informationA separate file that includes three figures and six tables.