Evolution in fossil time series reconciles observations in micro- and macroevolution.

Area of Science:

• Evolutionary biology
• Paleontology
• Quantitative genetics

Background:

• Microevolutionary models often assume fixed adaptive landscapes, limiting their explanatory power for long-term phenotypic diversification.
• Macroevolutionary changes likely involve dynamic shifts in adaptive landscapes, necessitating models that account for this.
• Bridging the gap between microevolution and macroevolution requires understanding how adaptive landscapes change over time.

Purpose of the Study:

• To analyze high-resolution fossil diatom time series using models of changing adaptive landscapes.
• To investigate how different adaptive landscape dynamics influence phenotypic evolution over several hundred thousand years.
• To reconcile short-term and long-term evolutionary dynamics in fossil lineages.

Main Methods:

• Analysis of two exceptionally high-quality fossil diatom time series.
• Application of evolutionary models incorporating different adaptive landscape behaviors.
• Inference of trait evolution and adaptive landscape dynamics over paleontological timescales.

Main Results:

• One diatom lineage evolved on a randomly and continuously changing adaptive landscape.
• The second lineage exhibited a rapid shift in its adaptive peak, comparable to species-level differentiation.
• Both lineages displayed rapid, erratic evolutionary change, constantly readapting to optimal trait states.

Conclusions:

• Phenotypic evolution over extended timescales results from both gradual and sudden adaptive landscape repositioning.
• Fossil diatom trait evolution over hundreds of thousands of years is a composite of short-term and long-term dynamics.
• The findings suggest that contemporary evolutionary dynamics may reflect processes occurring over much longer timescales.