Tuesday, Aug. 10, 2010
When discussing how one species evolved into two or more distinct species, scientists often surmise that the uplift of mountains, which split populations of plants and animals, was the major contributing factor.
Not so fast, says Utah State University entomologist James Pitts.
“You might especially expect this of plants and animals in the desert, where the terrain is typically isolated by mountain ranges,” he says. “But for some organisms, species variation appears to have happened much more recently and the evidence points to glaciations that occurred during the Ice Age.”
An assistant professor in USU’s Department of Biology, Pitts studies velvet ants, members of the Mutillidae family. His research on velvet ant evolution during periods of glaciation appears in the report “Evolution of the nocturnal Nearctic Sphaeropthalminae velvet ants (Hymenoptera: Mutillidae) driven by Neogene orogeny and Pleistocene glaciations.” The paper was published in the July 2010 issue of Molecular Phylogenetics and Evolution.
Velvet ants are, in fact, not ants, but wasps, says Pitts, who joined USU’s faculty in 2005. He’s the only entomologist in North America conducting research on the creatures and publishing results in academic journals. Throughout the world, he’s one of five scientists who actively studies these solitary insects.
“Female velvet ants lack wings so they resemble ants,” he says. “The ‘velvet’ part of their name comes from the dense, velvety hair that covers their bodies.”
Pitts’ research for the paper focused on varied nocturnal velvet ant species, such as those found in Utah’s sand dune-studded Warner Valley. He collects specimens from the desert region that lies about 10 miles southeast of St. George.
“Unlike many other velvet ant species that are brightly colored, nocturnal velvet ants are a dull, light brown color,” he says. “
Using molecular data collected from current-day velvet ants and morphological data collected from fossils, Pitts and his students employed mathematical algorithms to assign probable dates of origin to each branch of the known Multillidae family tree.
“We used a molecular clock-like approach to construct a molecular phylogeny for Multillidae lineages,” he says. “This information, coupled with the fossil data, helped us determine when various species emerged.”
The findings support the idea that glacial action, some two million to as little as 10,000 years ago, separated groups of velvet ants and led to the formation of distinct species. This is considerably more recent than time periods when the Rocky Mountains and the Colorado Plateau arose.
“We naively thought that, once we determined the probable age of the species, we could easily match that information to known geological events,” Pitts says. “What we discovered is that the geological community is far from agreement on the time that specific geographical events occurred.”
Even so, his research reveals that roughly one third of velvet ant species emerged during the Ice Age.
His findings are somewhat surprising. Most studies of species variation have been done on mammals and plants, he says, which have longer life spans and generations than insects. A generation for the velvet ant is one year.
“You can’t make a sweeping claim that mountains caused all species variation,” Pitts says.
To date, more than 5,000 species of velvet ants have been identified. Pitts can take credit for naming more than 100. Has he named any of them after himself?
“Now, that would be very pompous of me,” says the evolutionary biologist, who, ironically, grew up playing on the grounds of Tennessee’s Rhea County Courthouse, site of the infamous 1925 Scopes “Monkey” Trial.
Instead, Pitts chooses rather esoteric monikers based on heroes of Finnish mythology or his favorite mystery writers.
Just recently, he received a thank you message from Icelandic novelist Arnaldur Indridason, for whom Pitts named a species, Sphaeropthalma arnalduri.
“What great and unexpected news — I don't know what to say,” Indridason wrote. “I just saw a picture of the thing and it must be the ugliest creature on the planet but I love it.”
“Because species have been named that we have no known specimens for, we have to be careful not to duplicate existing names,” Pitts says. “I simply choose lesser known names and add an ‘i’ to conform to scientific nomenclature.”
Pitts notes that velvet ants, which pack a ferocious sting and are known as “cow killers” in parts of the country, have no known predators.
“Velvet ants are very abundant and are probably much more ecologically significant than we give them credit for,” he says.
Writer: Mary-Ann Muffoletto, 435-797-3517, email@example.com