COMPLEX TRADE-OFFS AND THE EVOLUTION OF STARVATION RESISTANCE IN DROSOPHILA MELANOGASTER

Area of Science:

• Evolutionary Biology
• Genetics
• Physiology

Background:

• Trade-offs complicate evolutionary measurements when selection acts on multiple adaptations or life stages.
• Understanding these trade-offs is crucial for predicting evolutionary responses to environmental stress.

Purpose of the Study:

• To investigate physiological and life-history trade-offs across life-cycle stages in Drosophila melanogaster selected for starvation resistance.
• To determine the role of pre-adult stages in the evolution of adult stress resistance.

Main Methods:

• Surveyed 10 populations of Drosophila melanogaster selected for starvation resistance over 60 generations, along with controls and ancestors.
• Measured starvation resistance, development time, viability, weight, and lipid content.

Main Results:

• Selected flies showed 4-6 times longer starvation resistance in adults and 80% increased resistance upon eclosion.
• Larval and pupal stages exhibited significantly longer development and lower viability.
• Starvation resistance was linearly correlated with lipid content; larval lipid acquisition was key to adult resistance, but incurred costs.

Conclusions:

• Selection for stress resistance in one life stage can have significant, pleiotropic effects on other stages.
• Larval lipid acquisition is a major factor in the evolution of adult starvation resistance, albeit with fitness costs.
• Genetic correlation patterns may be misleading without resolving multiple pleiotropic interconnections.