In his research, McPeek was intrigued by the problem presented to scientists by damselflies, which are insects similar to dragonflies, he said. As many as ten distinct damselfly species can exist in a single pond, McPeek said, and experiments show that the only significant difference between the populations is the shape of their reproductive plates. In his research, McPeek sought to determine why speciation the divergence of one species into two distinct species would occur when the species appear to be so similar.
"The fundamental problem that I try to explain is how many species live on this planet and why it's a pretty simple question," McPeek said.
McPeek cited a single stream in Spain that supported 109 species across 58 different genera as an example of an apparently simple ecological system that contains extraordinary diversity.
McPeek hypothesized that the damselflies were divided into different species because past glacial development and geographic change temporarily isolated certain populations of the insects. This isolation could have kept the damselflies from breeding with each other for a period of time, leading to genetic drift and sexual divisions among the different species.
To test his hypothesis, McPeek used techniques from phylogeography, which examines genetic change across different geographic regions. His research demonstrated that rapid climate change caused by glacial development could be the reason for genetic divergence that occurs when species migrate, he said.
"The signature of species movement on Earth is written into every species we sample," he said.
By using a "molecular clock model" a measurement based on standard changes in certain organic molecules over time to estimate how long ago species diverged, McPeek discovered a correlation between species divergence and periods of glacial thaw. He added that while there appears to be a correlation, his research contains a significant margin of error.
McPeek criticized the way many scientists study the evolution of species under the assumption that organisms interact in a static system. The definition of coexistence as the ability of two species to persist indefinitely with each other is "a silly criterion to have," because it does not take into account the constantly shifting factors present in any given environment, he said.
"Our whole theoretical edifice is based around the assumption that things don't change," McPeek said.
McPeek argued that the process of evolution moves more quickly than many scientists believe. As glaciers melt and reform roughly every 100,000 years, species become periodically isolated into separate populations, which can lead to genetic divergence.
"Eighty percent of species are less than 10 million years old and 40 percent of them are less than two million years old," he said.
To understand the divergence of the damselfly species further, McPeek and his research team are developing computer-generated models of male and female damselfly pairs to study how they mate, he said.
In order to successfully mate, male flies must be able to attach to plates on the backs of female flies, which vary in shape across different damselfly species, McPeek said. Since damselflies cannot distinguish members of their own species from those of other species, female clamp recognition ensures that intra-species copulation does not occur.
The models will show how the damselflies clamp together and allow the researchers to measure the differences in shapes of reproductive parts mathematically, which will show how speciation occurs.
"I spend most of my time digitizing these parts if you were an insect you'd think this was pornography to learn to describe them mathematically," he said.
McPeek said that damselfly enthusiasts across North America send him specimens they gather, which he uses in his research.
In an interview with The Dartmouth, McPeek expressed his enthusiasm that his research on damselflies can be applied to many aspects of evolutionary research.
"I have the best job in the world," he said.
