http://www.nature.com/news/gut-microbes-keep-species-apart-1.13408
Brucker and Bordenstein addressed this by studying Nasonia giraulti and Nasonia vitripennis, two parasitic wasps that deposit their eggs in the larvae of other insects. The two species diverged one million years ago, and can still raise their young on the same hosts. When they breed, around 90% of male offspring die as larvae.
The researchers found that the wasps' gut microbes included a bacterium in the genus Providencia, and another species called Proteus mirabilis. The parental species had more Providencia, but P. mirabilis dominated in the hybrids. This suggests that interbreeding brings about harmful changes to the gut flora, so that the insects' microbiota helps to keep the two species separate.
To confirm that the different flora was responsible for the males' demise, the team tried ‘curing’ the hybrid wasps of their gut microbes. They devised a way of rearing Nasonia eggs in a nutrient broth rather than an insect host, and killed the microbes in the wasps' developing guts using antibiotics. This rescued many of the doomed hybrids: half survived to pupation. But when the team added Providencia and P. mirabilis to the rearing liquid of initially germ-free wasps, most of the hybrid larvae died as usual.
Genes and germs
“This is an important and potentially groundbreaking study,” says Jack Werren, an evolutionary geneticist at the University of Rochester in New York. “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.” The next step, he says, is to “determine which genes are involved in regulating which bacteria, and how this is disrupted in hybrids”.
Brucker and Bordenstein found that 40% of the wasps’ immune genes were at least twice as active in the normal hybrids as in the germ-free ones. They suspect that genetic incompatibilities between the parent species disrupt the hybrids’ immune systems and weaken their ability to control their gut microbes. The insects end up with an unusual microbiome, which kills them. “The closest analogy we have is that it’s like an autoimmune disorder,” says Brucker.
http://www.nature.com/news/gut-microbes-keep-species-apart-1.13408
Brucker and Bordenstein addressed this by studying Nasonia giraulti and Nasonia vitripennis, two parasitic wasps that deposit their eggs in the larvae of other insects. The two species diverged one million years ago, and can still raise their young on the same hosts. When they breed, around 90% of male offspring die as larvae.
The researchers found that the wasps' gut microbes included a bacterium in the genus Providencia, and another species called Proteus mirabilis. The parental species had more Providencia, but P. mirabilis dominated in the hybrids. This suggests that interbreeding brings about harmful changes to the gut flora, so that the insects' microbiota helps to keep the two species separate.
To confirm that the different flora was responsible for the males' demise, the team tried ‘curing’ the hybrid wasps of their gut microbes. They devised a way of rearing Nasonia eggs in a nutrient broth rather than an insect host, and killed the microbes in the wasps' developing guts using antibiotics. This rescued many of the doomed hybrids: half survived to pupation. But when the team added Providencia and P. mirabilis to the rearing liquid of initially germ-free wasps, most of the hybrid larvae died as usual.
Genes and germs
“This is an important and potentially groundbreaking study,” says Jack Werren, an evolutionary geneticist at the University of Rochester in New York. “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.” The next step, he says, is to “determine which genes are involved in regulating which bacteria, and how this is disrupted in hybrids”.
Brucker and Bordenstein found that 40% of the wasps’ immune genes were at least twice as active in the normal hybrids as in the germ-free ones. They suspect that genetic incompatibilities between the parent species disrupt the hybrids’ immune systems and weaken their ability to control their gut microbes. The insects end up with an unusual microbiome, which kills them. “The closest analogy we have is that it’s like an autoimmune disorder,” says Brucker.
http://www.nature.com/news/gut-microbes-keep-species-apart-1.13408