Ants are ubiquitous around the globe, with over 14,000 different species currently found on every continent except Antarctica. With an estimated four quadrillion individual ants on Earth, scientists have long wondered how ants became so successful.
Now, a new study published in the journal Evolution Letters has shed new light on this mystery by exploring how ants and plants have evolved together over the past 60 million years.
“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,” said study lead author Matthew Nelsen, a research scientist at the Field Museum in Chicago.
By combining fossils, DNA, and data on the habitat preferences of modern species, the experts reconstructed the evolutionary paths of ants and flowering plants, or angiosperms. They found that these paths were deeply intertwined, with the spread of angiosperms from forests coinciding with the movement of ants into new habitats.
About 60 million years ago, some of the plants in forests began to release more water vapor through tiny holes in their leaves. This created a wetter environment that encouraged ants to move their nests out from underground and up into the trees. This movement coincided with other organisms, such as frogs, snakes, and epiphytic plants, taking to the trees as well, creating new arboreal communities.
As some of the flowering plants moved outward into drier regions, some ants followed in search of the food opportunities provided by these plants.
“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,” Nelsen explained.
Moreover, when ants take the seeds to get the elaiosomes, they help disperse them – a clear win for the parent plants – which highlights the mutual benefits of the relationship between ants and plants.
These findings are particularly relevant given the current climate and biodiversity crises that our planet is facing.
“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,” Nelsen concluded.
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