Some algae have been hanging together rather than going it alone much longer than previously thought, according to new research.
Ancestors of Volvox algae made the transition from being a single-celled organism to becoming a multicellular colony at least 200 million years ago, during the Triassic Period.
At that time, Earth was a hot-house world whose inhabitants included tree ferns, dinosaurs and early mammals. Previous estimates had suggested Volvox's ancestors arose only 50 million years ago.
The algae switched to a communal lifestyle in only 35 million years -- "a geological eyeblink," said lead researcher Matthew D. Herron of The University of Arizona in Tucson.
Figuring out how algae made the leap can provide clues to how multicellular organisms such as plants and animals evolved from single cells.
Cooperating successfully is the key, Herron said.
"All the macroscopic organisms we see around us trace back to unicellular ancestors," said Herron, a doctoral candidate in the UA's department of ecology and evolutionary biology. "Each of those groups had to go through a transition like this one.
"We think the early changes in this process were related to cooperation among cells and conflicts among cells -- and finally to the resolution of those conflicts," he said.
The researchers used DNA sequences from about 45 different species of Volvox and related species to reconstruct the group's family tree and determine how long ago the first colonial ancestor arose.
The team's article "Triassic origin and early radiation of multicellular volvocine algae," is in this week's online Early Edition of the Proceedings of the National Academy of Sciences.
Herron's co-authors Jeremiah D. Hackett and Richard E. Michod are members of the UA's department of ecology and evolutionary biology. Co-author Frank O. Aylward was at the UA when the research
|Contact: Mari N. Jensen|
University of Arizona