Major habitat changes, such as landward movement from the sea, are key evolutionary events that often trigger bursts of diversity. Until recently, the frequency of these habitat transitions in the eukaryotic tree of life, which includes animals, plants, and a vast array of microbes, was unclear. Today, an international research team led by Uppsala University in Sweden found that eukaryotes have made hundreds of major leaps from sea to land and freshwater habitats, and vice versa, over the during their evolution over the last two billion years.
“We found that organisms in the eukaryotic tree of life are generally grouped by whether they live in the oceans or in non-marine habitats such as fresh water and soils. This finding confirms that adaptation to higher salinity different – or crossing the salt barrier – is difficult even for microbes,” said study lead author Mahwash Jamy, an expert in organismal biology at Uppsala.
“However, we have found that microbial eukaryotes have been able to successfully establish themselves in new habitats several hundred times during their evolution, and we will likely uncover more of these transitional events as we sequence microbes to from a greater number of locations.It is likely that these difficult-to-achieve transitions allowed colonizing organisms to occupy vacant ecological niches, leading to the great diversity of eukaryotes we see today.
By sequencing the DNA of microbes from boreal lakes, forest floors, the Indian Ocean, the Mariana Trench and various other environments, scientists have reconstructed large evolutionary trees that have revealed major patterns in evolution habitat preference. “It is likely that two of the largest groups of eukaryotes, called SAR and Obozoa, each of which is much larger than the plant and animal kingdoms, arose in completely different habitats,” the lead author explained. study, Fabien Burki, associate professor of organismal biology. in Upsala.
“The SAR lineage, which includes groups like diatoms, ciliates, dinoflagellates, radiolarians, etc., first appeared in the Precambrian oceans. On the other hand, the ancestral Obazoan, which now diverse in fungi, animals, choanoflagellates, and amoebozoans, probably inhabited non-marine habitats.
These results suggest that the change in salinity between marine and non-marine habitats played a crucial role in shaping eukaryotic evolution. Further research is needed to determine what genetic mechanisms underlie these seminal evolutionary events.
The study is published in the journal Nature ecology and evolution.
By Andrei Ionescu, Terre.com Personal editor