Speaker
Description
Theoretical models suggest that when the environment fluctuates slowly over hundreds of generations, populations primarily adapt to the environmental optimum through genetic changes rather than relying on phenotypic plasticity. Experimental evolution shows that gradual environmental change promotes the accumulation of smaller-effect mutations, leading to greater fitness than adapting to a single drastic environmental change. Long-term studies confirm continuous mutation accumulation over time. Here we conduct a long-term evolutionary experiment with slowly fluctuating environments using experimental populations of fission yeast founded from a single clone. We gradually introduce and intensify the stress in the environment, then return equally slowly to the initial conditions without the stressor. By sequencing the populations, we will determine whether adaptation occurs primarily through genetic changes or phenotypic plasticity. We predict that when the environment starts to change back, instead of reverting their changes, compensatory mutations that eliminate any possible trade-offs with the original environment will be fixed. When compared to populations evolved under constant conditions, we can determine whether environmental fluctuations promote genetic divergence. To test whether accumulated mutations actively contribute to adaptation, we will compare the growth rates of evolved and ancestral populations across different environments. Our findings will reveal whether environmental fluctuations promote genetic divergence and compensatory adaptation, shedding light on how populations genetically respond to slow and reversible environmental change.