Beautiful Butterflies

How do you make a new species? Scientists are on the trail of the answer to that question.

Researchers working at the Smithsonian Tropical Research Institute in Panama have apparently copied one possible form of speciation in the laboratory, maybe even recreating the evolutionary steps that took place in birth of a species. In the wild, a species called Heliconius heurippa looks suspiciously like a blend between the two species H. cydno and H. melpomene. To see whether H. heurippa may have resulted from a process called hybridization, the scientists brought H. cydno and H. melpomene into the lab for breeding. After just three generations of interbreeding the two species, the scientists had an intermediate color form of butterfly that exactly matched H. heurippa individuals in the wild. Genetic analysis also supported that they had produced a strain of butterfly genetically distinct from either of the parent species.

That’s fine, but what about breeding? Usually some sort of isolation has to occur for a species to become truly distinct as a species or else it will eventually blend back into the parent populations remaining only an occassional variant form. Well, it turns out that H. heurippa is reproductively isolated, which means that its reproductive behavior doesn’t usually lead it to mate with any but its own kind. The researchers found that when given a choice of mating with H. cydno, H. melpomene, or H. heurippa females, males chose H. heurippa 75-90% of the time. This suggests that this sort of natural reproductive isolation might occur quite often in nature allowing hybrids to branch off and become a separate species.

Hybridization is an interesting occurrence, which can lead one to question the defined boundaries of species. Many times in nature the process results in reproductively inviable individuals, like the mule, but can sometimes lead to perfectly viable animals. Dogs, cats, and birds are often hybridized by breeders in order to create new strains for pet enthusiasts. After time, hybrids can be considered their own species if they don’t tend to mate with dissimilar individuals for either behavioral or physical reasons. But, if they maintain that ability to even a slight degree what does it mean for speciation, and to that end for conservation?

Are animals that maintain some amount of reproductive connectedness with other members of their genus or species more or less likely to weather changes to their environment? Does it matter if a hybrid species like H. heurippa goes extinct as long as the probable parent species remain extant? How much information will be necessary to make such a decision as we learn more and more about genetics and the complexities of speciation? Where will we start to draw lines?

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