C4 photosynthesis and climate through the lens of optimality

<p>Post-processed climate model output and associated source code for "C4 photosynthesis and climate through the lens of optimality".  Data files are in netcdf format, ncl source code, and README file included.</p>

<p><u><strong>Article Abstract</strong></u></p>

<p>CO<sub>2</sub>, temperature, water availability and light intensity were all potential selective pressures to propel the initial evolution and global expansion of C<sub>4</sub> photosynthesis over the last 30 million years. To tease apart how the primary selective pressures varied along this evolutionary trajectory, we coupled photosynthesis and hydraulics models while optimizing photosynthesis over stomatal resistance and leaf/fine-root allocation. We further examined the importance of resource (e.g. nitrogen) reallocation from the dark to the light reactions during and after the initial formation of C<sub>4</sub>syndrome. We show here that the primary selective pressures − all acting upon photorespiration in C<sub>3</sub> progenitors − changed through the course of C<sub>4</sub> evolution. The higher stomatal resistance and leaf-to-root allocation ratio enabled by the C<sub>4</sub> carbon-concentrating mechanism led to a C<sub>4</sub> advantage without any change in hydraulic properties, but selection on nitrogen reallocation varied. Water limitation was the primary driver for the initial evolution of C<sub>4</sub> 25-32 million years ago, and could positively select for C<sub>4</sub> evolution with atmospheric CO<sub>2</sub> as high as 600 ppm. Under these high CO<sub>2</sub> conditions, nitrogen reallocation was necessary. Low CO<sub>2</sub> and light intensity, but not nitrogen reallocation, were the primary drivers during the global radiation of C<sub>4</sub> 5-10 MYA. Finally, our results suggest that identifying the predominate selective pressures at the time C<sub>4</sub> first evolved within a lineage should help explain current biogeographical distributions.</p>

<p><br />
Zhou, Haoran, Brent Helliker, and Erol Akcay. 2018. C<sub>4</sub> Photosynthesis and Climate through the Lens of Optimality. bioRxiv doi: 10.1101/048900.</p>