While mountains, rivers and oceans can act as physical barriers that keep animals from cross-breeding, an evolutionary process known as speciation, new research reveals that the trillions of microbes found in the gut of animals may play the same very important role, Nature reports.
Biologists Robert Brucker and Seth Bordenstein of Vanderbilt University studied the gut bacteria of two divergent wasp species that diverged about 1 million years ago, and found that gut microbes act as an evolutionary barrier that prevents the wasps, and other animals, from cross-breeding, thus resulting in the creation of new species.
Subtle differences in the gut microbes of the wasps means that when the two species cross-breed, their hybrids develop a distorted microbiome, resulting in a shortened life-span.
The scientists hypothesized that incompatible DNA was responsible for the wasp offsprings' early deaths. They found that 40 percent of the wasps' immune genes were at least twice as active in the normal hyrbrids as compared to the germ-free ones.
"The closest analogy we have is that it's like an autoimmune disorder," said Brucker.
Could gut microbes be nature's way of preventing divergent species from breeding, thus partially responsible for the creation of new species?
"This is the most convincing evidence that the microbiome evolves with hosts over long time periods and might affect the speciation process," Bordenstein said of the study's results published in Science.
John Werren, a biologist at the University of Rochester in New York, called the new study "important and potentially groundbreaking," explaining that scientists have studied "speciation...for many years, and this opens up a whole new aspect to it."
"It reveals that problems in hybrids can be due not just to their genetic make-up, but to interactions between their genes and associated microbes," Warren said, adding that the next step is to "determine which genes are involved in regulating which bacteria, and how this is disrupted in hybrids".
"We'd never say that the microbiome is the key element in all speciation," said Brucker. "Our classic understanding of speciation is still true but we're just adding a new arm to that."
