People often think that the devastating collision of the city-sized asteroid Chicxulub with North America 66 million years ago is simply a mass extinction event, which, of course, it was for the dinosaurs. But a growing body of research is arguing that the pall of death and darkness left behind by Chicxulub turned out to be a boon not only for smaller mammals, but also for giant fungi, exotic deep-sea life forms and, now, the increasing colonization of Earth by ant species. Today, more than 15,000 species of ants dot the world, and their queens rule a vast empire hidden underground (and also inside dead trees or other suitable places). Evolutionary biologists and genomics researchers, collaborating between Germany, China and Denmark, have identified several independent bursts in the diversification of ant species dating back to the early Paleogene, just after the Chicxulub impact. Their new study attributes the rise of ant biodiversity to transposable DNA elements similar to retroviruses, sometimes called “jumping genes.” “The asteroid impact had dramatic consequences for the environment,” the study’s lead author, Lukas Schrader, a professor of molecular evolutionary biology at the University of Münster, Germany, said in a statement. “We have now found the genomic mechanism that connects these ecological disorders with the subsequent rapid diversification of ants: transposable elements.” Going Viral Scientists used to think of transposable elements (TEs) as effectively “genomic parasites,” given the tendency of this DNA to spread from host to host, seemingly as an end in itself, offering no clear evolutionary advantage. Some studies have shown that some TEs are even suspected of contributing to diseases themselves, including some cancers and neurological disorders. But more recently biologists have detected comparable spikes in species diversification, sometimes with the promise of new ecological niches or greater resilience, in the lineages of several animals, including primates and bats. A 2021 study on the urban mosquito species Anopheles coluzzii from sub-Saharan Africa, for example, found that TEs had helped these little bloodsuckers protect themselves against insecticides. “I think we will see more and more cases where TEs will help explain cases of rapid adaptive changes,” as Schrader told The Scientist in 2022, during an earlier phase of his research into how these viral genes benefit ants, that is, all insects in the family Formicidae. Schrader and his co-authors compared the genomes of 163 ant species taken from a dozen of the 16 Formicidae subfamilies known to still exist today. This reconstruction of the evolutionary history of these species helped generate something of a timeline of the main jumping genetic activity over the last 100 million years. It revealed that, among other features, TEs helped stimulate the generation of new odorant receptors (OR) and taste receptors (GR) critical for the ants’ use of chemicals to communicate and perceive their environment. “Therefore, TEs likely provided the raw genetic material that facilitated diversification, while the ecological opportunities generated by the extinction event determined how this variation might have consequences,” Schrader’s team explained last month in the journal Science Advances. History of Ants Beyond the boost that TEs provided to ant species during the Paleogene, these virus-like genes have also continued to drive ants’ evolutionary resilience into the modern era. Schrader’s work with colleagues at the Institute for Evolution and Biodiversity at the University of Münster, as well as with collaborators abroad, found that those ant lineages they tracked with the highest number of jumping genes also tended to produce a more diverse number of descendant species today. Schrader’s team acknowledged that there are still some unknown factors, including the possibility that some extinct ant species have “shown different patterns of TE activity,” which could have altered this study’s assessment of how jumping genes have helped ants adapt. There is also the mystery of the origins of the type of ants before the 100 million year time frame of this study: “[We] “We cannot exclude the possibility that as-yet-unknown TE bursts may have affected the earliest history of ant diversification,” the researchers said.
