Population dynamics of metastable growth-rate phenotypes

Area of Science:

• Evolutionary biology
• Cellular dynamics
• Population genetics

Background:

• Traditional evolutionary models assume distinct time-scales for mutation and reproduction.
• Laboratory evolution experiments typically focus on the fixation of beneficial mutations.
• Recent research highlights the complexity of genotype-phenotype transformations and epigenetic inheritance.

Purpose of the Study:

• To investigate novel population dynamics influenced by intracellular processes.
• To examine how intracellular mechanisms affect population structure and adaptation.
• To challenge the separation of time-scales in Neo-Darwinian evolution.

Main Methods:

• Studying adaptation dynamics in genetically rewired yeast cells.
• Measuring growth rates and phenotypic distributions over >100 generations.
• Analyzing fluctuations in cell populations under constant environmental conditions.

Main Results:

• Observed a wide distribution of growth rates coexisting for extended periods (>100 generations).
• Fastest-growing cells did not dominate the population as predicted by simple selection.
• Significant, long-timescale fluctuations in cellular phenotypes (growth rate, protein content) were detected.

Conclusions:

• Intracellular processes play a crucial role in shaping population structure, challenging the Neo-Darwinian paradigm.
• Cellular phenotypic states are metastable, with variations occurring over generational time-scales.
• A new framework is needed for population dynamics that integrates intracellular and population-level processes.