How Pheidole Ants Achieved World Domination

Ants belonging to the genus Pheidole, which make up about one tenth of the global ant population, have managed to achieve world domination, according to a new study.

"If you go into any tropical forest and take a stroll, you will step on one of these ants," Evan Economo, Okinawa Institute of Science and Technology (OIST) Graduate University, said in a statement.

About 1,200 Pheidole species are found on Earth, living in ecosystems ranging from rainforests to deserts, all of them close relatives. They may be widespread, but until now scientists did not know in detail how species of Pheidole evolved and spread across Earth. So to shed some light on how ants of this genus conquered new lands, Economo and colleagues at the University of Michigan compared gene sequences from 300 Pheidole species.

Their findings, published in the Proceedings of the Royal Society Series B, suggest that this group of ants evolved the same way twice - once to take over the New World, or the Americas, and then again to take over the Old World - Europe, Asia, Africa, and Australia - essentially achieving world domination.

"The new world and the old world are almost completely independent of each other," Economo explained. "Pheidole first evolved in the new world, from one species to over six hundred species." Then, one of those ants colonized the old world, where it evolved into another six hundred or so ant species.

You might think that several different movements took place over the years to result in hundreds of Pheidole species living on every continent today. However, researchers say that that would mean they would have had to find closely related species living in diverse continents. Rather, Pheidole simply split into two main groups.

"They are dominant in certain areas preferentially to others," Economo added, "and these patterns are consistent even though they evolved independently."

So why do researchers care so much about ants' family tree? Well, they may seem like tiny, inconsequential insects, but they actually serve a very important purpose in various ecosystems. For one, ants are abundant in most terrestrial ecosystems and make up as much biomass as all vertebrates combined. They also play vital roles in soil aeration, nutrient cycling and dispersing plant seeds. And because they are found all over the world, Pheidole ants in particular help scientists better understand the various habitats that they live in.

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