Ants spread all over the world by following flowering plants out of prehistoric forests, suggests a new study.
Today there are more than 14,000 different species, spread over every continent except Antarctica.
American researchers have estimated that there are more than four quadrillion individual ants on Earth: 4,000,000,000,000,000 of them.
But how ants evolved to become so ubiquitous has remained a mystery until now.
Scientists used a combination of fossils, DNA, and data on the habitat preferences of modern species to piece together how ants and plants have been evolving together over the past 60 million years.
The findings, published in the journal Evolution Letters, suggest that when flowering plants spread out from forests, the ants followed, kicking off the evolutionary process.
Study lead author Dr. Matthew Nelsen said: “When you look around the world today, you can see ants on nearly every continent occupying all these different habitats, and even different dimensions of those habitats – some ants live underground, some live in the canopies of trees.
“We’re trying to understand how they were able to diversify from a single common ancestor to occupy all these different spaces.”
Scientists already knew that ants and flowering plants, or angiosperms, both originated around 140 million years ago and subsequently became more prevalent and spread to new habitats.
Nelsen and his colleagues wanted to find evidence that the two groups’ evolutionary paths were linked.
He and his colleagues compared the climates that 1,400 modern ant species inhabit, including data on temperature and precipitation.
They coupled that information with a time-scaled reconstruction of the ant family tree, based on genetic information and ant fossils preserved in amber.
Nelsen explained that many ant behaviors, such as where they build their nests and what habitats they live in, appear to be deeply ingrained in their species’ lineages, to the point that scientists are able to make pretty good guesses about prehistoric ants’ lives based on their modern relatives.
The data, when paired with similar information about plants, helped bring the early ants’ world into focus.
About 60 million years ago, ants lived primarily in forests and built their nests underground.
Nelsen, a research scientist at the Field Museum in Chicago, said: “Around this time, some of the plants in these forests evolved to exhale more water vapor out through tiny holes in their leaves – they made the whole place a lot wetter, so the environment became more like a rainforest.”
He said that In the wetter environment, some of the ants began moving their nests out from underground and up into the trees. Frogs, snakes, and some plants also took to the trees around that time, helping create new arboreal communities.
Some of the flowering plants living in the forests began to spread outward, inching their way into more arid regions and adapting to thrive in drier conditions.
Nelsen and his colleagues’ work suggests that when flowering plants left the forests, some of the ants followed.
He believes some of the plants may have provided an incentive for the ants in the form of food.
Nelsen said: “Other scientists have shown that plants in these arid habitats were evolving ways of making food for ants – including things like elaiosomes, which are like fleshy appendages on the seeds.
“And when ants take the seeds to get the elaiosomes, they help disperse them: a win for the parent plants.”
The researchers say that by showing how plants helped shape the evolution and spread of ants is especially important in light of current climate change.
Nelsen added: “This study shows the important role that plants play in shaping ecosystems.
“Shifts in plant communities – such as those we are seeing as a consequence of historic and modern climate change – can cascade and impact the animals and other organisms relying on these plants.”
Produced in association with SWNS Talker
