Extending evolutionary forecasts across bacterial species.

Area of Science:

• Evolutionary biology
• Microbial adaptation
• Genomics

Background:

• Evolutionary forecasting aims to predict species adaptation to selective pressures.
• Evolve-and-resequence experiments with multiple species are crucial for testing broad evolutionary principles.
• Understanding cross-species adaptation requires analyzing genetic divergence and fitness landscapes.

Purpose of the Study:

• To test the extendibility of evolutionary forecasts across different species.
• To investigate the genetic basis of adaptation to static culture conditions in Pseudomonas species.
• To identify factors limiting detailed molecular predictability in evolutionary forecasts.

Main Methods:

• Evolve-and-resequence experiments were conducted on Pseudomonas syringae and Pseudomonas savastanoi.
• Adaptation to static culture conditions was monitored.
• Mutational patterns and gene-level differences were analyzed.
• The relative fitness of mutants was compared between species.

Main Results:

• Both species evolved biofilm mutants with a wrinkly spreader phenotype, primarily due to mutations in the wsp operon.
• Mutational patterns differed between species, explained by a lack of conserved relative fitness of mutants.
• Conserved mutation hotspots were identified, potentially increasing parallel evolution.
• Predictability was limited on a detailed molecular level due to genotype-phenotype-fitness map differences and mutational biases.

Conclusions:

• Evolutionary forecasts can be extended across species for predicting adaptation.
• Differences in genotype-phenotype-fitness maps and mutational biases constrain detailed molecular predictability.
• Conserved mutation hotspots can drive parallel evolution across species.