Although phenotypic plasticity can be advantageous in fluctuating environments, it may come too late if the environment changes fast. Complementary chromatic adaptation is a colorful form of phenotypic plasticity, where cyanobacteria tune their pigment composition to the prevailing light spectrum. In this presentation, we show that the time scale of phenotypic plasticity plays a key role in phytoplankton competition under fluctuating conditions. We developed a resource competition model, with green and red picocyanobacteria and a third cyanobacterium that can adapt its color to the prevailing light conditions. The latter species will be called the flexible phenotype, which could change its color in about 7 days. The model predictions were tested in competition experiments, in which the color of the incident light switched between red and green at different frequencies.

Results/Conclusions

Model simulations and competition experiments show that the flexible phenotype was much more successful when it had sufficient time to fully adjust its pigmentation. Thus, the flexible phenotype benefited from phenotypic plasticity only when fluctuations in light color were relatively slow, corresponding to slow mixing processes or infrequent storms in their natural habitat. In total, our results provide experimental evidence that the time scale of phenotypic plasticity affects competitive communities and their diversity in fluctuating environments.