— The proud parents Lycaeides Melissa and L. ida (left and middle) gave rise to a new species of butterfly (right) that is able to mate successfully (Image: James Fordyce)
A new butterfly species that lives high in the Sierra Nevada mountains of the western US has turned out to be a rare creature indeed: it arose through the merging of two distinct species. It is one of very few hybrid species that can successfully breed.
Lycaeides Melissa and Lycaeides idas the genetically distinct butterfly species that initially gave rise to the new hybrids do not regularly mate. But Zachariah Gompert at Texas State University in San Marcos, US, and colleagues found that when they do mate, they produce offspring that are able to breed with each other and produce further generations.
It is an unusual finding. Normally, new species will arise as offshoots of existing ones. The branches of the evolutionary tree do not typically merge.
The new species of butterfly, which is yet to be named, possesses a mosaic genome that is a mixture of its two parental genomes yet which is evolutionarily "younger" than either, Gompert says. What is more, this offspring cannot reproduce with either of its parent species, he adds.
The researchers suggest that the new species may have emerged through natural selection for an extreme environment in this case, a high-alpine habitat. Its evolutionary parents, L. melissa and L. idas occupy habitats at different altitudes.
L. melissa lives in the Great Basin on the east side of the mountains, while L. idas occupies wet meadows at mid-elevation on the west side. The new species lives above the tree line, in between these two parental species.
It is not the first time that scientists have observed this in butterfly species. In June 2006, another study revealed that a wild species of the brightly coloured Heliconius butterfly in South America arose via the merger of two related species (see Hybrids: When two species become three).
Journal reference: Science (DOI: 10.1126/science.1135875)