Identifying the Elephant in the Room
DNA barcoding is a tool that aids in species identification. Detecting and analyzing a short fragment of DNA allows comparison to a reference database that is a catalog of a species’ DNA barcodes. Thus, a sample that is otherwise unidentifiable may be able to have its species origin identified. This has found application in DNA forensics.
At the San Diego Zoo Institute for Conservation Research, research efforts in elephant conservation have provided an opportunity to collect blood samples from wild elephants in several African locations. We have been producing DNA barcodes for these elephants as an initial frame of reference for adding information that may be useful for combating ivory poaching.
By identifying the geographic source of a specimen—or even the identity of an individual whose tusks were poached—local and international law enforcement agencies may be able to prosecute poachers and obtain convictions.
When we recently analyzed samples from three elephants that lived in Masai Mara National Reserve in Kenya, the DNA barcodes we produced revealed an important aspect of the recent evolutionary history of elephants in Africa.
Recent DNA studies of living African and Asian elephants, as well as the extinct woolly mammoth, have clarified that there are two species of elephants in Africa, the savannah elephant and the forest elephant. Although they are closely related, recent evidence indicates they diverged 2.5 – 5.0 million years ago, about as long as the time of the divergence between Asian elephants and wooly mammoths.
Interestingly, Asian elephants are more closely related to the extinct woolly mammoth than they are to either species of African elephant.
It is clear from DNA evidence that the two species of African elephants have interbred in the past, following their divergence. The evidence for this comes from genetic characteristics that are maternally inherited, that is, from mothers to their offspring, but only their daughters can pass on the characteristic. We found that the three elephants from Masai Mara had a maternally inherited characteristic, their mitochondrial DNA sequences, that were typical for forest elephants, although the elephants of Masai Mara are large and typical in appearance to savannah elephants.
It is really quite amazing to see how, sometimes unexpectedly, new tools of genetic analyses provide surprising findings. We now know that savannah and forest elephants evolved independently, but exchanged genes in the past. The evidence for this is embedded in their genomes and we are learning to read this information. Our studies contribute to expanding the knowledge of elephant genetic variation that can provide support to conservation efforts and potentially aid in anti-poaching law enforcement operations.
Oliver Ryder, Ph.D., Director of Genetics Division