A molecular timescale for eukaryote evolution with implications for the origin of red algal-derived plastids.

Strassert JFH, Irisarri I, Williams TA, Burki F

Nat Commun 12 (1) 1879 [2021-03-25; online 2021-03-25]

In modern oceans, eukaryotic phytoplankton is dominated by lineages with red algal-derived plastids such as diatoms, dinoflagellates, and coccolithophores. Despite the ecological importance of these groups and many others representing a huge diversity of forms and lifestyles, we still lack a comprehensive understanding of their evolution and how they obtained their plastids. New hypotheses have emerged to explain the acquisition of red algal-derived plastids by serial endosymbiosis, but the chronology of these putative independent plastid acquisitions remains untested. Here, we establish a timeframe for the origin of red algal-derived plastids under scenarios of serial endosymbiosis, using Bayesian molecular clock analyses applied on a phylogenomic dataset with broad sampling of eukaryote diversity. We find that the hypotheses of serial endosymbiosis are chronologically possible, as the stem lineages of all red plastid-containing groups overlap in time. This period in the Meso- and Neoproterozoic Eras set the stage for the later expansion to dominance of red algal-derived primary production in the contemporary oceans, which profoundly altered the global geochemical and ecological conditions of the Earth.

Fabien Burki

Fellows programme

PubMed 33767194

DOI 10.1038/s41467-021-22044-z

Crossref 10.1038/s41467-021-22044-z

pii: 10.1038/s41467-021-22044-z
pmc: PMC7994803
figshare: 10.6084/m9.figshare.12417881.v2