Density-dependent selection in Drosophila: evolution of egg size and hatching time

Area of Science:

• Evolutionary biology
• Animal behavior
• Population genetics

Background:

• Laboratory studies on Drosophila adaptation to larval crowding consistently show evolved preadult competitive ability.
• However, the specific traits conferring this ability vary depending on the experimental conditions of crowding.

Purpose of the Study:

• To investigate the evolution of egg size and hatching time in Drosophila populations adapted to different larval crowding regimes.
• To identify consistent correlates of evolved competitive ability across varying selection pressures.

Main Methods:

• Populations of Drosophila were adapted to three distinct larval crowding conditions.
• Egg size and hatching time were measured in these adapted populations and compared to ancestral control populations.
• Egg size and hatching time were assayed on three sets of populations adapted to larval crowding and their low density ancestral control populations.

Main Results:

• All crowding-adapted Drosophila populations evolved larger egg size compared to controls.
• Egg size emerged as a consistent correlate of evolved larval competitive ability across different crowding regimes.
• Crowded populations exhibited shorter average egg hatching times, with significance observed under high feeding band density.

Conclusions:

• Egg size is a crucial and consistent trait in the evolution of Drosophila larval competitive ability under crowding.
• The details of larval crowding, including feeding band density, influence which adaptive traits evolve.
• Experimental designs incorporating multiple selection regimes provide nuanced insights into adaptive evolutionary trajectories.