Preliminary investigations into reproductive fitness and sexual conflict in drosophila populations selected for rapid pre-adult development and early reproduction

Abstract

Development is a key phase in the life-history of an organism since it influences traits affecting survival and reproduction from birth till death, and, thereby Darwinian fitness, especially in holometabolous insects in which pre-adult development is a major resource acquiring phase (Chippindale et al.,1994, 1997, 2003). Theory suggests that an ‘ideal’ life-history would be one that maximizes all fitness components. If there were no constraints on the evolution of traits, an ideal organism would take infinitesimally small time to develop and reach reproductive maturity, and keep reproducing infinitely at a high rate. However, such ‘ideal’ life histories are not seen in living organisms. Hence, trade-offs are central to the study of life-history evolution since these determine the constraints that prevent maximization of all fitness components simultaneously. All else being equal, an organism should develop and attain reproductive maturity as fast as possible since individuals with a shorter generation time would have a fitness advantage over those with a longer generation time (Roff, 1992). Consequently it has been of interest to try and understand the constraints on evolving rapid development to reproductive maturity. One approach to do this has been to select populations of Drosophila melanogaster for rapid pre-adult development, leading to overall reduction in the generation time, and examine the correlated evolution of various life-history related traits in such populations (Zwaan et al., 1995; Nunney, 1996; Chippindale et al., 1997; Prasad et al., 2000).