Science

A DNA study traces connection between elephant species & why the elephant’s population is declining

Why African elephant's population is declining: a study towards conservation of these species
TSAVO EAST, KENYA, MAY 2011: Images of some of the last of the great Elephant tuskers in Africa, taken in Tsavo East 18 May, 2011. Massive elephant poaching in recent years has seen most of the mature bull elephant population of African countries decimated for their ivory. A Tusker is defined as an elephant with a set of 100 pound ivory tusks, or therabouts. This depletion of the elephant gene pool is having a negative effect on populations, with weak dna being passed on instead of the strongest. (Photo by Brent Stirton/Reportage for National Geographic Magazine.)

A dedicated team of researchers conducted a study spanning over a decade to distinguish between the species of African elephants, interbreeding and complexities, and the danger that lies ahead if interbreeding between two of the three species of elephants isn’t initiated at the earliest. According to the study published in Proceedings of National Academy of Science, two of the three elephant species are endangered. Apparently, unlike any other elephant or animal species, two major elephant species have not interbred from past half a million years which has pushed these species in the list of endangered animals.

Researchers from Uppsala University, McMaster University, Harvard Medical School, Broad Institute of MIT and Harvard, and the University of Potsdam studied various species of elephants and their genetic makeup which eventually gave them an insight on their ancestors and the danger that lies in the near-future. During the study, the team was able to test genetic evidence of interbreeding before elephant species wiz ancestors of mammoths, mastodons, and modern-elephants occurred in the Pleistocene Epoch. By definition, Pleistocene Epoch was the last ice age period that occurred 2.6 million years ago and continued for 11,700 years followed by Holocene Epoch (modern stage).

The study found that ancestors of three elephants species interbred with other species in the Elephantidae family in an attempt to cope up with the changing climate to support evolution. Further, in the study, it is believed that two of the three species never mated with other species. These are forest elephants and savanna elephants who have never mated with any species in the Elephantidae family. These species as per scientists will be endangered if they continue not to interbreed. The process of mating with other species of the same family i.e. interbreeding is paramount as it maintains genetic diversity needed to evolve. The study has pinpointed towards the importance of interbreeding as a noble criterion towards controlling the ever decreasing population of species.

The research team comprising of members from elite research institutes and universities conducted a genome study where 14 genomes were picked from extinct species of elephants from Africa and Asia, two American Mastodons, a Columbian Mammoth, 120,000-year-old straight-tusked elephant and modern elephants. The genomes underwent DNA sequencing which revealed that mastodons, mammoths interbreed with the ancestors of modern Asian and African elephants. The study also discovered a gene flow between mastodons, mammoths, and ancestors of modern elephants and also, the history that followed in the evolutionary paradigm. The scientists were surprised after they found out that the two species which never mated lived in close geographical proximity yet maintained isolation for over half a million years.

Excerpt from Wikipedia
In 2008, the International Union for Conservation of Nature (IUCN) declared African elephants as vulnerable. Following the population chart of African elephants, there were approximately 1.3 million African elephants (upper limit of 3.0 million) in 1979. By the end of 1989, the population declined to 609,000 which is a staggering decline of 74% in population (1977 to 1989). As per the data, loss of savannah elephants accelerated in 1987 with a total of 80% decline in population as opposed to 43% for forest elephants. As per Wikipedia, although elephants receive a certain degree of protection in each country they are found, more than 70% of these elephants lived outside the ‘protected’ areas. Following the decline in the population of African elephants, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) listed this species under Appendix I that makes its trade illegal.

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