In a first, Japanese researchers have compared gene sequences from 300 species of Pheidole – world’s most species-rich ant genus. About one tenth of the world’s ants are close relatives; they all belong to just one genus out of 323, called Pheidole. It suggests that Pheidole evolved the same way twice, once to take over the New World and then again to take over the Old World.
The team from Okinawa Institute of Science and Technology Graduate University used gene sequences to construct a tree that shows when and where each species evolved into new species.
At the same time, in a parallel effort, they scoured the academic literature, museums around the world, and large databases to aggregate data on where all 1,200 or so Pheidole species live on Earth, creating a range map for each species.
“If you go into any tropical forest and take a stroll, you will step on one of these ants,” said professor Evan Economo.
The new world and the old world are almost completely independent of each other.
“Pheidole first evolved in the new world, from one species to over 600 species. Then, one of those ants colonised the old world where it evolved into another 600 or so ant species,” added Economo.
Till now, researchers have never had a global perspective of how the many species of Pheidole evolved and spread across the Earth.
The new work will help scientists get a better handle on these organisms that are dominant features of many of Earth’s ecosystems.
Pheidole species also show a climate pattern: there tend to be more Pheidole in warm, wet climates. “They are dominant in certain areas preferentially to others,” Economo said, “and these patterns are consistent even though they evolved independently.” This suggests that evolution repeated itself, and is to some extent deterministic. That is, there is likely a reason why Pheidole dominate tropical ecosystems: they didn’t just become successful due to random chance. “One idea is that they have a key innovation, something that gives them an advantage over other species,” said Economo. “That certainly could be true but we don’t know what that advantage is at this point.”
The results were published in the journal Proceedings of the Royal Society Series B.
Evan P. Economo, Pavel Klimov, Eli M. Sarnat, Benoit Guénard, Michael D. Weiser, Beatrice Lecroq, L. Lacey Knowles. Global phylogenetic structure of the hyperdiverse ant genus Pheidole reveals the repeated evolution of macroecological patterns. Proc. R. Soc. B:2015282 20141416;DOI: 10.1098/rspb.2014.1416.Published 26 November 2014