Response to Comment on ‘‘The Evolution of Modern

Falkowski et al. (1) examined when, why, and how a diverse group of eukaryotic phy-toplankton, which overwhelmingly contain red plastids, rose to ecological prominence in Mesozoic time and continue to dominate the contemporary oceans. Our analysis included the fossil record of thecate dinoflagellates, coccolithophores, and diatoms; biochemical composition of extant taxa and their phylo-genetic relationships; geochemical recon-structions of ocean paleochemistry; eustatic changes in sea level; and ecosystem inter-actions. One facet in our analysis was the portable plastid hypothesis (2), which was included to accommodate the observatio