The Tasmanian devil (Sarcophilus harrisii), the world's largest surviving carnivorous marsupial, is endangered by a fatal transmissible disease called devil facial tumor disease (DFTD). DFTD is a naturally occurring infectious cancer first observed on the east coast of Tasmania in 1996. This cancer is rapidly spreading across the island, the devil's only native habitat. DFTD is predicted to spread throughout Tasmania within 5 years. Because the disease has a 100% mortality rate, preservationists are concerned that the devil may face imminent extinction.

Credit: Ralph Loesche

It has been suggested that low genetic diversity among Tasmanian devils has contributed to the success of DFTD. Efforts to conserve the species include captive breeding programs to maintain a group of devils that could be re-released into the wild to repopulate the island after DFTD has run its course. Recently, an international group of researchers led by Webb Miller and Stephan C. Shuster (Pennsylvania State University, University Park) and Vanessa M. Hayes (Children's Cancer Institute Australia and University of New South Wales, Australia) contributed to the conservation effort by using a revolutionary approach. They sequenced the genomes of two Tasmanian devils from opposite ends of the animal's native range, as well as the genome of a DFTD tumor isolated from one of the devils ((Proc. Natl. Acad. Sci. USA doi:10.1073/pnas.1102838108; published online 27 June 2011). They also analyzed a set of genetic markers from 175 additional devils, some of which were museum specimens. The sequencing project had a two-part goal: first, to quantify genetic diversity within the population and evaluate whether it has decreased during recent history, and second, to identify which animals should be selected for inclusion in captive breeding programs in order to preserve the population's existing genetic diversity.

Their analysis indicates that the level of genetic diversity among Tasmanian devils has been relatively low and unchanged for more than 100 years, well before DFTD arose in the population. The researchers also suggest that animals included in captive breeding programs should be genetically characterized and selected to represent the full extent of genetic diversity among the population today.

The group expressed cautious optimism that Tasmanian devils can survive, given adequate habitat space, population size and preservation of existing genetic diversity through captive breeding. Furthermore, the scientists believe that this project exemplifies the potential of sequencing and genetic analysis to aid species preservation efforts. They hope this approach can be applied to other endangered species as well.