Quality–quantity trade‐offs drive functional trait evolution in a model microalgal ‘climate change winner’

Abstract

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 trade-off 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.

The evolution of trait correlations constrains phenotypic adaptation to high CO2in a eukaryotic alga

“…Building on this work, we create a trait landscape or 'trait-scape' for the green alga Chlamydomonas reinhardtii adaptation to high-CO2 using four independent and ecologically relevant traits (growth rate, respiration, cell size, and daughter cell production). Specifically, using the output from an experimental evolution study [3] with 5 genotypes of C. reinhardtii, we demonstrate that both the traits and the correlations between traits evolved between the low-CO2 environment (ancestral environment) and the high-CO2 environment (evolved environment) ( Fig. 2).…”

“…2). Specifically, all four traits changed to varying degrees depending on the genotype [3], and correlations between traits changed upon high-CO2…”

“…Ancestral and evolved trait values from low-CO2 and high-CO2 adapted populations across 5 genotypes of Chlamydomonas reinhardtii were downloaded from Lindberg et al (2020) [3] and can be found in Supplementary File 1. We selected four independent ecologically relevant traits: growth rate, respiration, cell size, and daughter cell production.…”

“…Particularly, there has been a significant increase in global change studies examining the roles of microbial evolution in shaping future biogeochemical cycles. This work has helped to more explicitly integrate the fields of evolution and microbial ecology resulting in both long-term experimental evolution studies with ecologically important microbes, and to a limited extent, the incorporation of adaptation into more ecological and ocean circulation models [1][2][3][4][5][6][7][8][9][10][11][12][13]. These studies are just the first step in tackling the immensely complex challenge of microbial evolution and its influence on global biogeochemistry.…”

Surviving heatwaves: thermal experience predicts life and death in a Southern Ocean diatom

“…Above Topt, one could reasonably suppose that cells would be stressed, and could accumulate damage, even if they are able to grow quickly in the short term, which is consistent with, for example, reactive oxygen associated with rapid growth due to CO2 enrichment (Lindberg & Collins, 2020). Below Topt, cells would be operating normally, and even if they are not under ideal conditions, it is unlikely that they are experiencing severe thermal stress.…”