Learning ability and longevity: a symmetrical evolutionary trade-off in Drosophila

Area of Science:

• Evolutionary biology
• Animal behavior
• Genetics

Background:

• Learning ability can be enhanced through artificial selection in various species.
• Despite adaptive advantages, the evolutionary potential for learning may be limited, suggesting potential costs.
• The costliness of learning has rarely been empirically tested.

Purpose of the Study:

• To investigate the correlated responses of life-history traits to artificial selection for improved learning in Drosophila melanogaster.
• To determine if there is an evolutionary trade-off between learning ability and longevity.

Main Methods:

• Artificial selection was applied to replicate populations of Drosophila melanogaster for improved learning ability.
• Life-history traits, including longevity, fecundity, and body mass, were measured in selected and control populations.
• Learning ability was assessed in populations selected for extended longevity using an olfactory conditioning assay.

Main Results:

• Populations selected for improved learning exhibited a 15% reduction in average lifespan compared to controls.
• A minor decrease in late-life fecundity and a slight increase in dry adult mass were observed in learning-selected flies.
• Selection for improved learning did not affect egg-to-adult viability, development rate, or desiccation resistance.
• Flies selected for extended longevity showed a significant (nearly 40%) reduction in early-life learning ability, which diminished with age.

Conclusions:

• A significant evolutionary trade-off exists between learning ability and longevity in Drosophila.
• Selection for enhanced learning comes at the cost of reduced lifespan.
• Selection for extended longevity incurs a cost in terms of reduced learning capacity, particularly early in life.