Madrid, 31 (Europe Press)
It is the result of an investigation based on a combination of fossils, DNA and data on the habitat preferences of modern species to reconstruct how ants and plants evolved together in the last 60 million years. The results are published in the journal Evolution Letters.
Ants pretty much everywhere. There are more than 14,000 different species, spread across every continent except Antarctica, and researchers have calculated that there are more than 4,000 trillion individual ants on Earth — that’s 4,000 followed by 12 zeros. But how ants evolved to conquer the world remains a mystery.
“Today, ants live on almost every continent, in different habitats and even in different dimensions: some live underground, others in the treetops. We are trying to understand how they managed to diversify from one common ancestor to occupy so many different spaces,” explains Matthew Nielsen, Research scientist at the Field Museum in Chicago (USA) and lead author of the article.
Scientists already knew that both ants and flowering plants, or angiosperms, arose about 140 million years ago and only then became more widespread and spread to new habitats. Nielsen and his colleagues wanted to find evidence that the two groups’ developmental trajectories were linked.
To find this link, Nielsen and his colleagues (Corey Morrow of Cornell University, Kevin Boyce of Stanford University, and Richard Ree of the Field Museum) compared the climates of 1,400 species of modern ants, including data on temperature and precipitation.
They related this information to a time-scale reconstruction of the ant family tree, based on genetic information and ant fossils preserved in amber.
Many ant behaviors, such as where they build their nests and the habitats they live in, appear to be so deeply ingrained in their species’ lineage that scientists are able to make fairly accurate guesses about the lives of prehistoric ants based on their modern relatives.
This data, along with similar information about plants, has helped us better understand the primitive ant world.
About 60 million years ago, ants lived mainly in forests and built their nests underground. “At that time, some plants in these forests have evolved to let out more water vapor through tiny holes in their leaves, making the whole place wetter and making the environment more like a tropical rainforest.” Nelson explains.
In this wetter environment, some ants have begun to move their nests from underground to trees. (They weren’t the only ones to move into the trees, either: Frogs, snakes, and random plants, similar to the bromeliads and air plants we have today, also took up residence in the trees around this time, helping to create new tree communities.)
Some of the flowering plants that lived in these forests began to spread outward, moving to drier regions and adapting to thrive in drier conditions.
Nielsen and colleagues’ work suggests that when flowering plants left the forests, some ants followed. The plants may have provided a stimulus in the form of food.
“Other scientists have shown that plants in these arid habitats evolved ways of feeding the ants, such as elaiosomes, which are like fleshy appendages,” Nielsen said. And when the ants grab the seeds to get the elaiosomes, they help disperse them.
The researchers say that showing how plants helped shape the evolution and spread of ants is especially important in light of the climate and biodiversity crises we face.
“This study demonstrates the important role that plants play in shaping ecosystems,” says Nielsen. “Changes in plant communities, such as those we see as a result of historical and recent climate change, can trickle down to animals and other organisms that depend on those plants.”