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).
