A weird new insight into how new species evolveS

When two populations of a species are separated for many generations, their genomes start to drift apart as they adapt to their different environments. Eventually they can become two distinct species. But new research now suggests it's not always incompatible DNA that halts interbreeding — sometimes it's incompatible gut microbes.

You've no doubt heard a lot about the microbiome by now. We know that the microbes inside our body outnumber our own cells 10 to 1. We also know that different species have their own makeup of gut microbes, and you can tell a chimpanzee from a person just by analyzing the bacteria in stool samples. Scientists are now beginning to understand the surprising consequences to related species having different gut microbes.

Researchers decided to look at what happens when different parasitic wasp species try to interbreed. When Nasonia giraulti and Nasonia longicornis (two closely related species) mate, their offspring survive just fine. But when either of the wasps breed with Nasonia vitripennis, which diverged from the other two species a million years ago, most of the males in the second generation die.

But the story is a bit more complicated that it appears at first glance. ScienceNOW explains:

Seth Bordenstein and Robert Brucker, biologists at Vanderbilt University in Nashville, wondered if the reason for this mortality went beyond incompatible DNA. They knew that the gut microbes in N. vitripennis differed from those in the other two species, and they suspected that these microbes could play a role in the offspring deaths. Indeed, when they raised all three species of Nasonia without gut microbes—by rearing them on sterile food—almost all the second generation offspring of matings between N. vitripennis and N. giraulti wasps survived. And when the scientists reintroduced bacteria into the germ-free wasps, most of their second-generation offspring died, the duo report online today in Science.

The researchers think the gut microbiome may be a key player in the development of new species. You can read more about this find over at ScienceNOW and check out the abstract of the study in Science. Or, listen to the researchers discuss their work in the video below.

Top image via Robert Brucker.