After years of believing that microbe taxa rarely die off because of their very large populations, a new study showed that bacteria go extinct at substantial rates, although appear to avoid the mass extinctions that have hit larger forms of life on Earth. Bacteria is the most ancient and widespread form of life on Earth.
The study conducted by a team of researchers from the University of British Columbia (UBC), Caltech, and Lawrence Berkeley National Laboratory was published on Monday in Nature Ecology and Evolution.
The researchers of the study found evidence that global bacterial diversity has mostly increased over the past 1bn years, with roughly constant or only slowly changing overall speciation and extinction rates when averaged over all clades. They estimated that global bacterial extinction rates are only slightly below their speciation rates and that only a small fraction of bacterial lineages that ever existed survived to the present.
The team of scientists used massive DNA sequencing and big data analysis to create the first evolutionary tree encompassing a large fraction of Earth’s bacteria over the past billion years. They also estimated between 1.4 and 1.9bn bacterial lineages existing on Earth today. They were also able to determine how that number has changed over the last billion years—with 45,000 to 95,000 extinctions in the last million years alone.
Stilianos Louca, a researcher with UBC’s Biodiversity Research Centre who led the study, said that “bacteria rarely fossilise, so we know very little about how the microbial landscape has evolved over time,” adding that “sequencing and math helped us fill in the bacterial family tree, map how they’ve diversified over time, and uncover their extinctions.”
“While modern bacterial diversity is undoubtedly high, it’s only a tiny snapshot of the diversity that evolution has generated over Earth’s history,” says Louca.