Quality-quantity tradeoffs drive functional trait evolution in a model microalgal “climate change winner”

Phytoplankton are the unicellular photosynthetic microbes that form the
base of aquatic ecosystems, and their responses to global change will
impact everything from food web dynamics to global nutrient cycles. Some
taxa respond to environmental change by increasing population growth rates
in the short-term, and are projected to increase in frequency over
decades. To gain insight into how these projected “climate change winners”
evolve, we grew populations of microalgae in ameliorated environments for
several hundred generations. Most populations evolved to allocate a
smaller proportion of carbon to growth while increasing their ability to
tolerate and metabolise reactive oxygen species (ROS). This tradeoff
drives the evolution of traits that underlie the ecological and
biogeochemical roles of phytoplankton. This offers evolutionary and a
metabolic frameworks for understanding trait evolution in projected
“climate change winners”, and suggests that short-term population booms
have the potential to be dampened or reversed when environmental
amelioration persists.