Phenotypic and molecular evolution across 10,000 generations in laboratory budding yeast populations

Area of Science:

• Evolutionary biology
• Microbial evolution
• Genetics

Background:

• Experimental evolution is a powerful tool to study adaptation.
• Understanding long-term evolutionary dynamics is crucial for predicting biological responses to environmental changes.

Purpose of the Study:

• To investigate the long-term consequences of adaptation in Saccharomyces cerevisiae.
• To characterize the genetic and phenotypic changes during prolonged experimental evolution.

Main Methods:

• Evolved 205 Saccharomyces cerevisiae populations (haploid and diploid) for approximately 10 million generations across three distinct environments.
• Measured fitness changes over time and performed whole-genome sequencing.

Main Results:

• Observed repeatable patterns of declining adaptability over generations.
• Detected a steady accumulation of mutations, widespread genetic parallelism, and historical contingency.
• Diploid populations showed fixation of heterozygous mutations and loss-of-heterozygosity events.
• Did not observe elevated mutation rates or long-term population coexistence, unlike in E. coli.

Conclusions:

• Phenotypic adaptation is linked to genetic changes, including mutation accumulation and parallelism.
• Evolutionary dynamics in yeast differ from E. coli, highlighting organism-specific and environment-specific factors.
• Distinguishes general evolutionary principles from system-specific adaptations.