[All-postdocs] Bioseminar - Greg Fournier

[Ana Velez]

Woods Hole Oceanographic Institution
Biology Department Seminar

Thursday, May 28, 2026 - 12:00 pm
Redfield Auditorium

Greg Fournier
Associate Professor of Geobiology, Massachusetts Institute of Technology

Resolving the Prochlorococcus Debate: New Age Estimates and Evolutionary Narratives
Earth has undergone several major planetary disruptions and transitions that challenged its continued habitability. These include major carbon cycle and climate disruptions associated with mass extinctions of complex life in the Phanerozoic, as well as earlier events that were likely similarly disruptive for simple eukaryotic and microbial life, most notably, Proterozoic "Snowball Earth" glaciation events. These events were especially challenging for phototrophs, which typically depend upon liquid water in surface environments exposed to sunlight. Microfossil, biomarker, and molecular clock evidence support that diverse groups of eukaryotic algae emerged before the Neoproterozoic Snowball Events during the Cryogenian and survived this period, demonstrating their resilience to extreme climate disruption and near-elimination of their environmental niches. Were marine microbial groups also able to survive this event, or does extant marine microbial planktonic diversity represent a more recent recovery? Most relevant to this question is the evolutionary history of Prochlorococcus and the closely related marine Synechococcus (SynPro), which today constitute about half of marine primary productivity. These groups lack a fossil or biomarker record, and previous molecular clock studies of cyanobacteria have recovered varying ages, ranging from the Tonian to the Paleozoic. Here, we show that multiple molecular clock analyses of single protein families having undergone horizontal gene transfer from eukaryotic algae to SynPro enable direct fossil calibration of SynPro using the eukaryotic microfossil record. We consistently recover posterior ages supporting marine SynPro diversifying shortly after the Neoproterozoic Snowball events, with Prochlorococcus evolving substantially later, during the Ordovician, at the same time as the Ordovician Biodiversification Event.
Biology Seminar Web Page<https://www.whoi.edu/what-we-do/understand/departments-centers-labs/bio/bio-highlights-events/>

For questions, contact:

Ana Maria Velez
Biology Pre-Award Administrative Associate
Ph: 508-289-2334
[signature_1005462319]

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