In the Mountains of Santa Cruz, California, is home of two species of mice that share habitat and genetic lineage, but have a very different social life. The mouse or Peromyscus californicus is monogamous, while the deer mouse (Peromyscus maniculatus) is sexually promiscuous. Studying their differences at the genetic level, U.S. researchers have shown that promiscuity helps strengthen the immune system.
Monogamy is a rare trait among mammals, present in only 5% of the species. But why promiscuity is so successful? Comparing these two rodents so close, Matthew MacManes and colleagues from the University of California at Berkeley have concluded that differences in the lifestyles of these two species have a direct impact on communities of bacteria that reside within reproductive tract of the female. And what’s more: these differences affect diversity in genes for rodents provide immunity against infectious diseases.
Specifically, the deer mice, sexually promiscuous, had twice the bacterial diversity that monogamous, and this, generation after generation, has strengthened the genome of the first. “The species, sexual habits, is in contact with more individuals and exposed to a greater variety of bacteria, so it has developed a more robust immune system,” says MacManes.
“The promiscuous mice, by virtue of their sexual system, are in contact with more individuals and are exposed to a lot more bacteria. They need a more robust immune system to fend off all of the bugs that they’re exposed to. The things an animal does, the way it behaves, and who it interacts with, are important to natural selection. These factors can cause immunogenes to evolve at a much faster rate, or slower in the case of monogamous mice. That connection is important and probably under-recognized.”
The results, published in PLoS One, confirmed that differences in social behavior induced evolutionary changes at the genetic level. In fact, the researcher also investigates how DNA is modified depending on other aspects of social behavior, such as the solitary life that lead some animals from the coexistence in large groups who opt for other species. “In the coming years we will see an explosion in studies that answer a question: how genes can control what we do and how we behave?” Suggests MacManes.
“Now that we have these new sequencing technologies, people are going to be really interested in looking at the mechanisms that underlie these behaviors. How might genes control what we do, and how we behave? We’re going to see an explosion in these studies where people start to understand the very basic genetic mechanism for all sorts of behaviors that we know are out there.”