A NEW species of butterfly has been created in laboratories by interbreeding two distinct species, offering new insights into how evolution takes place in the wild.
The experiment by British, Colombian and American scientists has offered the strongest evidence yet that two species can cross-breed to form a new one, a process that many experts had considered impossible. In the study, the team sought to recreate the evolutionary pathway that the scientists suspected had given rise to Heliconius heurippa, a South American butterfly with redorange and yellow-white stripes on its wings.
The colouring suggested that it might be a hybrid of two related varieties — Heliconius cydno, which has a yellow stripe, and Heliconius melpomene, which has a red one. To test the theory, they interbred the two species, creating a butterfly with the two-stripe pattern of H. heurippa within just three generations.
The hybrid butterflies chose to mate with others of similar colouring, an indicator that a separate species had formed.
Jesus Mavarez, of the Smithsonian Tropical Research Institute in Washington DC, who led the team, said: “If you cover the red or yellow stripe of a bicoloured hybrid female, hybrid males no longer find her the least bit attractive.”
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His colleague Chris Jiggins, of Edinburgh University, said: “Butterflies tend to choose partners that look like themselves. So, once the new pattern was established, these individuals have tended to mate with one another and shunned their parental species.”
The study, published today in the journal Nature, is the most convincing case yet of a process known as homoploid speciation, the researchers said.
While different breeds of the same species, such as dogs, can produce fertile offspring, this is not often true when different species mate, as in the case of mules, created by crossing a horse with a donkey. This gives hybrids a vast evolutionary disadvantage that usually prevents the formation of viable new species.