Flemish researchers uncover hidden evolution of seaweed
For the first time, evolutionary processes of marine seaweeds have been determined, thanks to research from UGent and Meise Botanic Garden
Unlocking the past
Led by Olivier De Clerck, head of UGent’s Phycology lab, and marine biologist Frederik Leliaert of Meise, the study was published today in the American journal PNAS: Proceedings of the National Academy of Sciences.
“Green algae emerged more than one billion years ago,” say the researchers in a statement. “At the beginning of their evolution, a split gave rise to two groups – one from which land plants later emerged, about 400 million years ago.”
The other gave rise to a wide diversity of green algae from fresh and marine waters, including the green seaweeds, which play a prominent role in marine ecosystems.
Interaction spurs evolution
Because of how old they are, the evolutionary relationships between different groups of green seaweeds are very difficult to resolve and have remained unknown. By comparing the genes of a large selection of green seaweeds, combined with data from fossils, the Flemish researchers have been able to clarify these relationships and identify crucial evolutionary events.
“The results indicate that green seaweeds diversified between 650 and 750 million years ago, at the end of the Neoproterozoic,” say the researchers. “This geological period was affected by two major glaciations in which ice caps reached the equator.”
The ancestors of green seaweeds survived these extreme climatic conditions in isolated refuges at the bottom of shallow seas. Isolation of millions of years resulted in the independent evolution of different green algal groups.
The proliferation of green seaweeds caused fundamental changes in shallow
After these glaciations came the Ediacaran period, during which temperatures rose, uncovering sea floors. In these conditions, green seaweeds were able to disperse and diversify.
An increased supply of nutrients and biological interactions, including being eaten by fish and other marine life, probably triggered the evolution towards growth in the different groups of green algae. This would have happened in multiple ways, like multicellularity and the evolution of giant cells.
“In turn, the proliferation of green seaweeds caused fundamental changes in shallow marine ecosystems,” the researchers conclude, “which likely played a key role in the evolution of marine animals.”
Photo: The strange world of the Ediacaran geological period (630 to 542 million years ago), when green seaweeds were able to diversify following the severe ice ages of the Cryogenian
©Ryan Somma/Wikimedia Commons