March 22, 2006 | By: Carol Lea Spence
LEXINGTON, KY.

University of Kentucky entomologist Mike Sharkey finds himself in a position most people wouldn’t envy – up to his ears in wasps.

As the principal investigator on a branch of a National Science Foundation program called Assembling the Tree of Life (ATOL), Sharkey is reconstructing the phylogeny, or evolutionary history, of the Hymenoptera, an insect order that includes wasps, bees, flies, and ants.

“The idea then being that that evolutionary history will give us a template to build a classification that is predictive. That will allow people, once they have identified something, to know a lot about its biology and life history,” said Sharkey.

Scientists working on the ATOL project focus on defining a basic skeleton of all the major groups of organisms, including each major insect order. It is a massive task, considering the diversity of life on this planet. To the layman, the sheer number of Hymenoptera – probably the largest group of organisms in the world in terms of the number of species – can be daunting.

“The Hymenoptera constitute 17.5 percent of all multicellular life in Europe,” Sharkey said, referring to a European study. “And insects as a whole constitute more than 50 percent. So amongst the insects, the two biggest orders are the beetles and the Hymenoptera. And the only places where they’ve done strict counts are in Europe and there the Hymenoptera outnumber the beetles.”

Sharkey isn’t working alone to classify such an enormous group of organisms. Under his direction are four co-principal investigators and six major labs scattered around the country, as well as approximately 40 researchers in the United States and around the globe.

The researchers gather diverse groups of Hymenoptera from all over the world and compare both the physical and genetic characteristics of the specimens. Specific attributes unique to a particular group provide evidence of their common ancestry and reveal their evolutionary history.

“For example,” said Sharkey, “we believe that there was one common ancestor to all mammals. The reason we believe that is because all mammals share certain characteristics that no other animals have. We have mammary glands and we have hair. We now group mammals together because we believe there was one common ancestor that had both hair and mammary glands and it gave rise to all other mammals through descent with modification and speciation. This is a more scientific, a simpler, hypothesis than suggesting that hair and mammary glands have developed independently multiple times in the history of life.”

The study can have far-reaching practical effects, particularly in the control of non-native pest species. The vast majority of Hymenoptera are parasitoids, insects that lay their eggs on top of or inside of other insects and kill them. They’re extremely important in the natural world to keep populations at normal levels. Many of the pest species of insects that are in the United States were imported accidentally from other areas of the world. Accurate classifications of predator insects can help scientists who are engaged in biologic control studies.

This is particularly important in areas of the world where the flora and fauna have evolved in a secluded environment. Isolated faunas such as those of Hawaii and Australia aren’t used to fighting it out with all kinds of other competitors, Sharkey said. When insects are imported accidentally from Eurasia, Europe and Asia into an isolated region, havoc can ensue. The newcomers often survived in their native locales by doing battle with all kinds of invasive species over millions of years and are consequently “pretty tough animals,” he said. In an environment with no serious competitors, they run rampant. In places like that, biological control is very important.

The classifications Sharkey and his fellow researchers are defining will allow other scientists to examine a set of insects and determine which of them is best suited for biological control. Selecting the proper parasitoid is vital. Many of the insects that emerge from pest insects in their native countries are actually hyperparasites, meaning they attack the parasites inside the pest, not the pest itself.

“So when you rear insects out of a pest insect after it’s died,” said Sharkey, “and then something comes out of it and you may think, oh that must be a wonderful thing – it must be killing the insect. But no, often they’re killing the actual organism that was killing the insect. Parasitoids have a plethora of different biologies. Some of them reproduce very quickly. Some of them are very slow in reproducing. Some of them are very host specific and others aren’t. All these biologies can be predicted with a good classification.”

Without a solid classification, disastrous results can occur. Sharkey related a cautionary tale about a species of fly that was released about 40 years ago as a solution to the gypsy moth problem in the northeastern part of the United States.

“Only they didn’t study its biology very carefully. And it attacks all of the spectacular big moths, not just gypsy moths, but the big Luna moths and the Polyphemus moths, those big beautiful ones. Their population levels have just crashed all over the Northeast because of this nasty animal. So it’s not just a matter of going out and grabbing things that come out of another insect, you have to be very familiar with the biology of it or you can cause more damage,” he explained.

Two years into the five-year study, Sharkey and his team are just beginning a long, ongoing process of discovery.

“The job is never-ending. There are how many species of Hymenoptera? I would predict at least a million species, thousands and thousands of genera, and 90 different families,” he said. “Our primary goal is just to get the 90 families in good order, but hopefully we will be able to get to deal with the next level, the subfamily level, as well. So in total we’re going to be dealing with something like a thousand different groups to create a template for the classification of the million Hymenoptera that exist.”

Contact: 

Mike Sharkey, (859) 257-9364