In this work, we integrate theoretical modeling, molecular simulation, and empirical analysis to identify and characterize evolutionary hysteresis. We first show how epistatic interactions create bistable fitness landscapes and structural hysteresis in a two-locus Wright-Fisher model, revealing two distinct hysteresis regimes under cyclic and noisy selection. Notably, an epistatically constrained population achieves maximal average fitness at an intermediate level of environmental stochasticity. We then extend this framework to more complex systems, demonstrating robust hysteresis loops in both a disordered multilocus model and in biophysically realistic simulations of protein structural flexibility. Finally, we present empirical evidence of evolutionary hysteresis. By analyzing two decades of metagenomic time-series data from freshwater C. Nanopelagicaceae experiencing strong seasonal temperature cycles, we find that approximately 63% of seasonally oscillating alleles exhibit nonzero loop area versus temperature, and a majority retain substantial area under any constant phase shift of temperature, inconsistent with a simple evolutionary lag. Together, our results establish hysteresis as a general, measurable feature of evolution with a potential for probing features of complex fitness landscapes.

Close

PrevNext

View figure in article

• Evolutionary & population dynamics
• Molecular evolution
• Proteins