Hamiltonian patterns of age-dependent adaptation to novel environments

Area of Science:

• Evolutionary biology
• Population genetics

Background:

• Natural selection's influence on adaptation is often assumed to be strongest in early life stages.
• The decline of natural selection with adult age suggests adaptation rates may also decrease over an organism's lifespan.

Purpose of the Study:

• To investigate age-dependent adaptation to novel environments.
• To determine how the strength of natural selection at different life stages influences adaptation rates.
• To test predictions using experimental evolution in Drosophila melanogaster.

Main Methods:

• Simulated age-dependent adaptation to assess theoretical outcomes.
• Conducted experimental evolution with Drosophila melanogaster populations adapting to a novel diet.
• Compared population performance on ancestral versus evolutionarily recent diets across different age groups.

Main Results:

• Simulations indicated rapid early-life adaptation but slow, incomplete later-life adaptation.
• Drosophila populations performed better on an ancestral diet only at later ages.
• Performance on a novel diet was poorest at earlier ages compared to a long-established diet.

Conclusions:

• The rate of adaptation to novel environments is scaled by the forces of natural selection.
• Age-dependent changes in natural selection significantly impact a population's adaptive capacity.
• Experimental evidence supports theoretical predictions of age-related adaptation dynamics.