It seems that they have actually originated some time around 140 or 168 million
years ago, supported by the evolution of the surrounding environment.
But these resilient insects, now found in terrestrial ecosystems the world over,
apparently began to diversify only about 100 million years ago in concert with
the flowering plants, the scientists say.
"This study integrates numerous fossil records and a large molecular data set
to infer the evolutionary radiation of ants, which have deeper roots than we
thought," said Chuck Lydeard, program director
in NSF's Division of Environmental Biology, which funded the research.
Led by biologists Corrie Moreau and Naomi Pierce of Harvard University, the researchers
reconstructed the ant family tree using DNA sequencing of six genes from 139
representative ant genera, encompassing 19 of 20 ant subfamilies around the world.
Moreau, Pierce and colleagues used a "molecular clock" calibrated with 43 fossils
distributed throughout the ant family tree to date key events in the evolution
of ants, providing a well-supported estimate for the age of modern lineages.
Their conclusion that modern-day ants arose 140 to 168 million years ago pushes
back the origin of ants at least 40 million years earlier than had previously
been believed based on estimates from the fossil record.
"Our results support the
hypothesis that ants were able to capitalize on the ecological opportunities
provided by flowering plants and the herbivorous insects that co-evolved with
them," said Pierce. The herbivorous insects that evolved alongside flowering
plants provided food for the ants.
The researchers found that the poorly known ant subfamily Leptanillinae is the
most ancient, followed by two broad groups known as the poneroids (predatory
hunting ants) and the formicoids (more familiar species such as pavement ants
and carpenter ants).
