Frequency dependence and the predictability of evolution in a changing environment.

Area of Science:

• Evolutionary biology
• Population genetics
• Ecological dynamics

Background:

• Frequency-dependent (FD) selection influences evolutionary trajectories by linking fitness to population composition.
• Negative frequency-dependent selection (NFDS) can maintain polymorphisms or drive frequency fluctuations.
• Previous studies often overlooked the impact of dynamic environments on FD selection.

Purpose of the Study:

• To investigate the interplay between frequency-dependent selection and temporally fluctuating environments.
• To determine how environmental dynamics affect population genetic change under FD selection.
• To clarify the conditions under which FD-driven fluctuations persist.

Main Methods:

• Analysis of population genetic models incorporating FD selection and environmental fluctuations.
• Utilized Lewontin's metric (slope of frequency change) to distinguish microevolutionary outcomes.
• Reviewed empirical examples of FD selection in ecological contexts.

Main Results:

• A slope metric (D) effectively distinguishes evolutionary outcomes, even in changing environments.
• Moderate NFDS (0 > D > -2) can sustain quasi-cycles fueled by noise or drift, buffering environmental responses.
• Strong NFDS (D < -2) can generate self-sustained cycles or chaos, limiting predictability.

Conclusions:

• The interaction between internal evolutionary dynamics and external environmental forcing is crucial for understanding evolution.
• Environmental fluctuations can modulate or be overwhelmed by FD selection, depending on its strength.
• Further systematic investigation is needed to predict evolutionary outcomes in complex, dynamic systems.