Butterfly Beauty Evolves

Seeing spots: Reed with buckeye butterfly. Photo: Les Todd

Elegant patterns on butterfly wings are one of the delightful ornaments of summer. But for scientists, they are also golden opportunities to study the intricacies of evolution. That's because the patterns represent a complex process by which the creatures evolve to attract mates and confuse predators.

Biologists Robert Reed, a Hargitt Fellow at Duke, and Michael Serfas, a graduate student at the University of Wisconsin at Madison, are using the power of genetic technology to delve more deeply into that machinery--adding new insight into its components. In an article in Current Biology last summer, they described a comparison among butterfly and moth species of two genes that control so-called "eyespot" patterns on the wings, which range from simple lines to fully rounded spots.

Among the species they studied were those with such evocative names as Gulf fritillary, cabbage white, hornworm moth, buckeye, painted lady, passion vine, and pink bollworm. The two genes they studied, less poetically named, were Notch and Distal-less, chosen because they are master regulators of many genes that govern eyespot development.

The researchers not only compared the activity of the two genes across species, but also took molecular "snapshots" of how the genes' activity changed over time as individual species developed their wing patterns. These analyses implicated Notch and Distal-less regulation in the very early stages of color-pattern development. However, the researchers also found no color patterns related to Notch or Distal-less activity among the moth species they studied.

The new findings represent only the beginning of the scientific story of Notch, Distal-less, and the evolution of color patterns, Reed says. How the two genes actually function to determine wing patterns is still a mystery. The scientists hope to gain new insights into the intricacies of evolution at the molecular level and the ways in which natural selection drives evolution.