Evolution

17
Jan

Hybrid Dolphin Gives Scientists Rare Window into Evolution

You’ve seen DNA analysis on every forensic criminology show on TV. Normally, it leads detectives to the killer, but in another case—this one on the open ocean—it has led scientists to a hybrid dolphin.

The clymene dolphin (Stenella clymene) is something of a biological riddle. Though these animals were first declared their own species by the American Society of Mammalogists in 1981, they were originally thought to be a subspecies of the spinner dolphin (S. longirostris), despite their similarities to the striped dolphin (S. coeruleoalba). DNA analysis has solved the puzzle, conclusively stating that clymene dolphins are a distinct species.

clymene_dolphin_image
Scientists recently discovered the clymene dolphin is a hybrid species.

In her study, Ana Amaral at the University of Lisbon collected both mitochondrial and nuclear DNA from 72 individuals of the three similar dolphin species. Mitochondrial DNA is passed on through the organism’s mother, whereas nuclear DNA comes from both parents. Here, analyzing both was key. In her analysis, Amaral found that the DNA from the nucleus was most similar to the spinner dolphin, while DNA from the mitochondria was most similar to the striped dolphin.

This suggests that the clymene dolphin is the product of crossbreeding striped and spinner dolphins—natural hybrid, something scientists know is rare but possible in wild animals. Hybrids are thought to be even rarer still in marine mammals, and before this study, hadn’t been previously documented. What’s more unusual was the fact that they produced not only viable offspring, but an entirely new species.

Charles Q. Choi, writing for National Geographic News:

“You need to have hybrids be as fit as the parental species, able to carve out their own ecological space,” explained [evolutionary ecologist Pamela Willis of the University of Victoria in Canada].

Then they somehow have to mate with only each other, rather than with either parental species, “hence allowing them to spin off onto their own, independent evolutionary trajectory and become a species of their own,” Willis added. “Both of these conditions are hard to meet.”

It’s a rare window into an evolutionary process that’s seldom seen in animals as advanced as cetaceans. Fortunately, we still have clymene dolphins around to witness it, though the situation for many dolphin species is increasingly dire.