When blowflies and flesh flies settle on dead animals, they aren’t just feasting on the carrion, they are in fact sampling their DNA. Scientists have demonstrated that this DNA persists long enough to be sequenced, allowing them to gain a quick and cost-effective snapshot of mammal diversity in otherwise inaccessible rainforest environments.
The scientists published their findings in the journal Molecular Ecology. Researchers stumbled upon this technique while they were studying a form of anthrax that kills chimpanzees in Côte d’Ivoire. They started to sample flies to see whether the anthrax bacterium could be harbored inside the flies feasting on infected bodies. They discovered that they were detecting mammalian DNA from the flies, which could also be used to assess biodiversity.
Sébastien Calvignac-Spencer, an evolutionary biologist at the Robert Koch Institute in Berlin, and his colleagues baited traps with meat. The team collected the carrion flies from the Taï National Park in Côte d’Ivoire and the Kirindy Reserve in Madagascar. They found that 40% of them carried mammal DNA. The material was sequenced and it was possible to identify 16 mammals in Côte d’Ivoire, including six of the nine local primate species, as well as Jentink’s duiker (Cephalophus jentinki), and endangered antelope of which there are less than 3,500 worldwide. In Madagascar, the team identified four mammal species, including two lemurs.
The team was able to recover fragments that were several base pairs long, which would be harder to find in other mammals as their guts are more efficient at breaking down food with acids and enzymes. Flies have a less sophisticated digestive system.
The flies could also help track the status of endangered populations more effectively. The Ebola virus killed off thousands of gorillas in the Republic of Congo and Gabon a decade ago, but active monitoring has only detected 44 carcasses. It’s a lot harder to monitor the die-offs of smaller mammals, like bats or rodents.
Reference: “Carrion fly-derived DNA as a tool for comprehensive and cost-effective assessment of mammalian biodiversity” by Sébastien Calvignac-Spencer, Kevin Merkel, Nadine Kutzner, Hjalmar Kühl, Christophe Boesch, Peter M. Kappeler, Sonja Metzger, Grit Schubert and Fabian H. Leendertz, 8 January 2013, Molecular Ecology.