Scientists at the Smithsonian Tropical Research Institute in Panama recently created a hybrid butterfly species, Heliconius heurippa, by crossing the species Heliconius cydno and Heliconius melpomene in a laboratory.

"We re-created the evolutionary steps that may have given rise to H. heurippa, a hybrid butterfly species," says Jesús Mavárez, a molecular evolution fellow at the Tropical Research Institute.

H. heurippa exists in the wild and is considered unusual because it is a fully sexual hybrid, capable of reproducing. It is only attracted to others of its kind and will not mate with either of its parent species. The experiment by Mavárez and co-researcher Mauricio Linares of the University of the Andes, Colombia, suggests that fully sexual hybrid species of animals may be more common than previously thought.

Butterflies in the genus Heliconius exhibit a tremendous diversity of brightly colored red, orange, yellow and white markings on black wings. Color patterns serve as mating cues for these butterflies, which are extremely choosy about finding mates with their own, species-specific, wing pattern.

Linares had long suspected that H. heurippa, boasting red and yellow wing stripes, could be a hybrid species resulting from a cross between H. cydno and H. melpomene. To test his theory, Linares designed and performed a series of crosses between H. cydno and H. melpomene.

"We found that a wing pattern almost identical to that of the hybrid can be obtained in just three generations of lab crosses between H. cydno and H. melpomene," he explains.

H. heurippa males choose females with red and yellow stripes. They don’t choose females of either of their parent species because these species have only a yellow or a red stripe. “If you cover the red or the yellow stripe of a bicolored hybrid female, hybrid males no longer find her the least bit attractive,” says Mavárez, who documented the genetic relationships between the three species at the Tropical Research Institute’s molecular biology laboratories in Panama.

The "weird" wing pattern of H. heurippa individuals makes them undesirable as mates for members of their parents’ species but attractive to each other. Such a preference is nearly all that is required for a new species to arise.