The subterranean termite Macrotermes gilvus is widespread across Southeast Asia, and has been throughout modern times. But, absent today’s human-aided transport of species across the globe, how did such a ground-dwelling insect get from mainland Myanmar all the way out to the islands of the Philippines, Indonesia, and Malaysia?
The answer lies in ancient land bridges that existed in eras when sea levels were lower, and researchers from Universiti Sains Malaysia (USM) say the genetic markers present in M. gilvus termites throughout varying Southeast Asia locales reveal the routes these termites—and many other terrestrial animals, as well as early humans—likely followed as they dispersed there over the past 2 million years.
USM’s G. Veera Singham, Ph.D., Ahmad Sofiman Othman, Ph.D., and Chow-Yang Lee, Ph.D., chose to analyze M. gilvus because it is currently widespread and because its regular dispersal flight range is short. Also, when it establishes new colonies, it depends on a particular soil structure and the availability of a fungal symbiont. “Therefore, the genetic signature of this species should reflect historical patterns rather than contemporary gene flow between different regions of Southeast Asia,” says Veera Singham.
The researchers collected termites from more than 200 populations of M. gilvus in regions across Southeast Asia and examined the genetic relationships between them using both mitochondrial genes and microsatellite markers.
In results published last week in PLOS ONE, Veera Singham, Othman, and Lee report that their phylogeographic analysis suggests a north-south dispersal corridor from Indochina to Java that existed between 1.09 million and 420,000 years ago, followed by a west-east dispersal route that existed between 870,000 and 340,000 years ago that allowed the termites to expand from the mainland toward the Philippines.
“Termites would have spread through these routes on their own in the ancient times, but later in the modern times their dispersal could have further aided by human activities,” says Lee. “The termite dispersal routes are indicative of the presence of suitable habitable environment during the glacial periods that were also suitable for other animals (such as mammals) and including early humans to exploit similar routes for migration and movement.”