What the fluc? How environmental predictability shapes plastic and evolutionary responses in marine and freshwater phytoplankton
The world is changing at unprecedented rates, increasingly exposing organisms not only to a change in the mean environment, but also to rare or extreme conditions and increased environmental variation. Theory shows that environmental fluctuations and the predictability thereof impacts on extinction dynamics and the evolution of phenotypic plasticity, i.e. the ability of one genotype to display various phenotypes as a response to environmental change. However, most experiments concerned with testing how evolution will act in novel environments are carried out in stable environments using single strains evolving on their own. This severely limiting our ability to test how plasticity, and variation of plasticity within populations of organisms, evolves and whether environmental change mainly affects the degrees to which ecology (i.e. abundances and species sorting), evolution, and plasticity interact to shape how organisms respond to changing environments. Here, I present work carried out using phytoplankton, the drivers of biogeochemical cycles and the fuel of food-webs. Phytoplankton were evolved in fluctuating environments for several hundreds of generations. Fluctuations were either natural (e.g. seasonality in pond systems and Baltic Sea surface waters), or highly controlled in laboratory environments. In the latter, we manipulated the frequency or the amplitude of the fluctuations. We find no cost of plasticity in the natural environments and in the environment where the fluctuations differed in amplitude, but not frequency. A marked conditional cost of plastic phenotypes was found the environment where fluctuations occurred at a fixed and highly predictable amplitude and frequency. Further, we show that average warming overrides the signal of seasonal fluctuations in the natural isolates.
Host: Gregor Kalinkat