Evolution of reproductive traits have no apparent life-history associated cost in populations of Drosophila melanogaster selected for cold shock resistance

In insect species like Drosophila melanogaster, the ability to evolve greater resistance or evolution of certain traits under specific environmental conditions leads to energy trade-offs with other important life-history traits. A number of studies from multiple fields have documented the life-history associated cost. However, no known studies have assessed the life-history associated cost with evolved reproductive traits and increase egg viability in cold shock selected population. To explore this, we used replicate populations of D. melanogaster that have evolved reproductive traits and egg viability in response to increased resistance to non lethal cold shock. To assess life-history cost; we measured longevity, life time fecundity, Larvae to adults development time, and larvae to adults survival. We found that there were no significant differences in longevity, life time fecundity, larvae to adults survival, and male body weight between the selected and control populations. However, selected populations have significantly longer pre adults developmental time compared to their control population. Females from the selected populations were bigger in size compared to the control populations. These findings suggest that there is no life-history cost associated with the evolution of greater resistance in the aspect of faster recovery of egg viability and reproductive traits post cold-shock. It quite possible the cost of the evolution of reproductive traits and egg viability in response to cold shock resistant is paid in terms of reduced resistance to other stresses