Significant links between photosynthetic capacity, atmospheric CO₂ and the diversification of C₃ plants during the last 80 million years

Abstract

Changing CO₂ concentrations will continue to affect plant growth with consequences for ecosystem functioning. The adaptive capacity of C₃ photosynthesis to changing CO₂ concentrations is, however, insufficiently investigated so far. Here, we focused on the phylogenetic dynamics of maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax)—two key determinants of photosynthetic capacity in C₃ plants—and their relation to deep-time dynamics in species diversification, speciation and atmospheric CO₂ concentrations during the last 80 million years. We observed positive relationships between photosynthetic capacity and species diversification as well as speciation rates. We furthermore observed a shift in the relationships between photosynthetic capacity, evolutionary dynamics and prehistoric CO₂ fluctuations about 30 million years ago. From this, we deduce strong links between photosynthetic capacity and evolutionary dynamics in C₃ plants. We furthermore conclude that low CO₂ environments in prehistory might have changed adaptive processes within the C₃ photosynthetic pathway.