Data from: Cell size, photosynthesis and the package effect: an artificial selection approach

Cell size correlates with most traits among phytoplankton species. Theory
predicts that larger cells should show poorer photosynthetic performance,
perhaps due to reduced intracellular self‐shading (i.e. package effect).
Yet current theory relies heavily on interspecific correlational
approaches and causal relationships between size and photosynthetic
machinery have remained untested. As a more direct test, we applied 250
generations of artificial selection (c. 20 months) to evolve the green
microalga Dunaliella teriolecta (Chlorophyta) toward different mean cell
sizes, while monitoring all major photosynthetic parameters. Evolving
larger sizes (> 1500% difference in volume) resulted in reduced
oxygen production per chlorophyll molecule – as predicted by the package
effect. However, large‐evolved cells showed substantially higher rates of
oxygen production – a finding unanticipated by current theory. In
addition, volume‐specific photosynthetic pigments increased with size
(Chla+b), while photo‐protectant pigments decreased (β‐carotene). Finally,
larger cells displayed higher growth performances and Fv/Fm, steeper
slopes of rapid light curves (α) and smaller light‐harvesting antennae
(σPSII) with higher connectivity (ρ). Overall, evolving a common ancestor
into different sizes showed that the photosynthetic characteristics of a
species coevolves with cell volume. Moreover, our experiment revealed a
trade‐off between chlorophyll‐specific (decreasing with size) and
volume‐specific (increasing with size) oxygen production in a cell.