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Successful merger of butterfly species

Researchers from the Smithsonian Tropical Research Institute (STRI) have recreated a real butterfly in the lab by crossing two other species of butterflies. In fact, this hybridization, which occurred without any changes to the chromosome number, could mean that it is an important factor in the origin of new animal species.

Researchers from the Smithsonian Tropical Research Institute (STRI) have recreated a real butterfly in the lab by crossing two other species of butterflies. This phenomenon, which is quite rare, is known as hybrid speciation. What is more surprising is that the hybrid butterfly has been created in just three generations of lab crosses. And BBC News tells us that the new butterfly species is a viable one, with its specific wing patterns which "make them undesirable as mates for members of their parent species." In fact, this hybridization, which occurred without any changes to the chromosome number, could mean that it is an important factor in the origin of new animal species. But read more...

Here are some quotes from the BBC News article.

A team of researchers from Panama, Colombia and the UK managed to recreate Heliconius heurippa in the laboratory by crossing two other species of butterfly; Heliconius cydno and Heliconius melpomene.
"The fact we've recreated this species in the lab provides a pretty convincing route by which the natural species came about," co-author Chris Jiggins, of the University of Edinburgh, told BBC News.
Jesus Mavarez, another author from the Smithsonian Tropical Research Institute in Panama, explained: "We found that a wing pattern almost identical to that of the hybrid can be obtained in months -- just three generations of lab crosses between H. cydno and H. melpomene.

The researchers have compared the morphology of reconstructed hybrids and wild H. heurippa. Here is one of the results below: "The shape of the forewing band was studied in 30 H. heurippa females and 37 H. heurippa-like lab hybrid females, using geometric morphometrics methods" (Credit: STRI/Nature).

Comparing hybrids and wild butterflies

This kind of hybrid speciation occurs also outside the labs, and scientists think it has already happened in Ragoletis fruit flies, swordtail fish, African cichlid fish and even American red wolves. But the recreation of Heliconius heurippa in the lab is quite different because the new species appears to be viable even if Mother Nature has done nothing.

Colour patterns on the wings of the butterflies may be crucial in forming new species, because they serve as mating cues. These butterflies are extremely choosey about finding mates with their own, species-specific wing pattern.
The wing patterns of H. heurippa individuals make them undesirable as mates for members of their parent species, but attractive to each other -- reinforcing patterns of mating that lead to a new species.

For more information, this research work has beeen published by Nature under the name "Speciation by hybridization in Heliconius butterflies" (Volume 441, Number 7095, Page 868). Here is the beginning of the Editor's summary, "Two into three does go."

Speciation is generally considered to result from the splitting of a single lineage into two, but recent research suggests that hybridization, where two ancestral taxa give rise to a third species by hybridization without a change in chromosome number, is a much more important motor for the origin of species than was realized. The phenomenon is still considered rare, but new examples are emerging. The latest is in the tropical butterfly Heliconius heurippa, known to have a hybrid genome, and which looks like a cross between two other species, H. cydno and H. melpomene.

And here are two links to the abstract and to some supplementary information (PDF format, 11 pages, 681 KB) from which the above illustration has been extracted.

Finally, here are some other references to this hybrid butterfly species.

Sources: BBC News Online, June 14, 2006; and various web sites

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