Evolution Promotes Resilience of Marine Mixotrophic Metabolic Strategies to Thermal Stress

Warming induces metabolic changes in microbial organisms, including increased respiration. Empirical studies have shown that evolution can compensate for thermal sensitivity and reduce respiration rate at high temperatures. Evolutionary adaptation may mitigate the effects of warming, but it remains unclear to what extent organisms can overcome thermodynamic constraints through evolution. Furthermore, evolutionary adaptations are modulated by interactions with plastic changes to respiration and other metabolic traits. 

We develop a mechanistic model including both evolution and metabolic plasticity to explore how adaptation to temperature affects variability in metabolic traits in mixotrophic marine microorganisms under thermal stress. By combining modeling with empirical data, we show that variability in metabolic activity between mixotrophs with different temperature histories can be explained by changes to the carbon budget facilitated by evolved reductions in respiration. The model suggests that evolution enhances thermal resilience over evolutionary timescales. Evolving mixotrophs exhibit less metabolic variability in response to temperature changes. In contrast, over shorter timescales plastic responses dominate over evolutionary adaptations, producing transient changes to metabolic activity following a temperature change. 

These results highlight the interplay between different biological adaptive mechanisms and provide a modeling framework for representing variability in microbial metabolism in the context of climate change.