'Cocktail' orangutans leave researchers shaken and stirred

Reintroduction of genetically distinct subspecies has led to hybridization in an endangered wild population

Date: February 25, 2016

Source: Max-Planck-Gesellschaft

Reintroduction of a genetically distinct subspecies has led to hybridization in an endangered wild orangutan population, report scientists. Inter-breeding animals from two genetically distinct populations can sometimes lead to 'hybrid vigor', in which offspring reap the benefits of their parents' individual qualities, they say.

As their natural habitats continue to be destroyed, increasing numbers of displaced endangered mammals are taken to sanctuaries and rehabilitation centres worldwide. The ultimate goal of these centres is often reintroduction: to return these animals to wild populations. In a new study published in Scientific Reports, however, Graham L Banes and Linda Vigilant of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, caution that such reintroductions can act as a form of genetic translocation. By using genetic analysis to assess a subset of historical reintroductions into Tanjung Puting National Park, Indonesia, they found that orang-utans from a non-native and genetically distinct subspecies were unwittingly released and have since hybridized with the Park's wild population. As orang-utan subspecies are thought to have diverged around 176,000 years ago, with marked differentiation over the last 80,000 years, the researchers highlight the potential for negative effects on the viability of populations already under threat.

When Biruté Galdikas and Rod Brindamour began their pioneering orang-utan rehabilitation efforts at Camp Leakey in Tanjung Puting National Park, Central Kalimantan, all orang-utans were considered a single species. Over 14 years, from 1971 to 1985, they released at least 90 orphaned and displaced apes into the surrounding wild population. Advances in morphological and genetic studies have since revealed two species of orang-utan, however, on the islands of Borneo and Sumatra. The Bornean orang-utan is further subdivided into three distinct, geographically and reproductively isolated subspecies, which last shared a common ancestor in the Pleistocene and have differentiated substantially over tens of thousands of years.

https://www.sciencedaily.com/releases/2016/02/160225135720.htm