Extinction and the temporal distribution of macroevolutionary bursts.

Area of Science:

• Evolutionary Biology
• Paleontology
• Population Ecology

Background:

• Phenotypic evolution over geological time is slower than predicted by microevolutionary rates, a phenomenon known as the paradox of stasis.
• Existing models propose stasis results from populations tracking stable adaptive peaks, but this doesn't explain the rarity of significant adaptive shifts.

Purpose of the Study:

• To investigate the role of adaptive peak dynamics and extinction in macroevolutionary stasis.
• To model how rapid peak movement, exceeding population adaptation rates, can lead to extinction and influence observed evolutionary patterns.

Main Methods:

• Developed a model incorporating explicit population dynamics and adaptive peak movement.
• Parameterized the model using published microevolutionary rate estimates.
• Simulated scenarios with varying peak displacement frequencies and magnitudes, including extinction events.

Main Results:

• Incorporating extinction significantly expands the parameter space that generates the appearance of stasis observed in empirical data.
• Extreme or frequent adaptive peak displacements rarely result in substantial trait evolution due to extinction.
• Larger peak displacements are infrequently inferred from trait data or fossil records because lineages typically go extinct.

Conclusions:

• Population ecology and extinction dynamics are critical factors in macroevolutionary patterns.
• The apparent constraint on phenotypic evolution in deep time may reflect the survival bias of lineages that happened to be on stable adaptive peaks.
• This provides an alternative explanation for the paradox of stasis, emphasizing the role of ecological factors in shaping long-term evolutionary trajectories.