Successful Merger of Butterfly Species
Roland Piquepaille writes "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. Read more for many additional references and a comparison of wing patterns between hybrids and wild butterflies."
Cane Toads?
The problem is that species is really only a very vaguely useful term. The line between "will not/cannot" breed with each other (and usually "in the wild" is added to this) is very very fuzzy, and there are many stages of compatibility in between, from sterile offspring, to rarely viable offspring, to rarely fertile offspring, and so on. Often species that will not breed in the wild under normal conditions will if conditions (or light levels, for instance) change.
"The butterflies COULD breed with each other, the scientists just don't think they will try."
As i noted, not reproducing without human intervention IS a barrier for defining speciation. That's why spinner dolphins and false killer whales are considered different species, even though wolphins exist in captivity. Chiclids, for instance, will only mate with certain colored fellow chiclids, but if you alter the light conditions so that they cannot make out the distinctions, then they will mate.
And so on.
One thing that I often find strange is that given the wide wide range of diversity amongst animals that are all of the same species (say, domestic dogs), people find it so hard to believe that speciation can happen, especially given that many genetically incompatible species are far far more similar to each other than dogs are morphologically. Two populations becoming genetically incompatible is really not much different from how they become visually different: it's just that the genetic changes in question happen to be working on more core reproductive elements rather than outward looks.
Sadly, there have been a number of cases. None of whom could fully integrated into society. Children raised by wolves, dogs, monkeys, and recently in the news... chickens (no really!).
See Feral Children for more information.
Not only a gray area, there is no real definition of species. The consensus seems to be something along the lines of "distinct population groups that generally don't interbreed". Not that they can't, not that they don't, just that they usually don't.
For example, I seem to recall that all (or maybe just most) of the members of the Canidae family (That's dogs, wolves, foxes, jackals etc.) can interbreed. I don't remember exactly though... it could have just been the Canis genus (dogs, wolves, jackals), or maybe I'm just mistaken. Anyone else know?