(Inside Science) -- The genome of the Tasmanian tiger (Thylacinus cynocephalus), or thylacine, supports its evolutionary position as the oldest carnivorous marsupial and reveals that a lack of genetic diversity caused its population decline, according to a new study published today in the journal Nature. The thylacine genome also suggests that the animal’s physical similarity to canids -- wolves, dogs and foxes -- isn’t because of shared genes.
Native to Australia, thylacines became extinct on the mainland 3,000 years ago. An isolated population survived on the island of Tasmania, until the early 20th century. The last known individual died in captivity at the Hobart Zoo in Tasmania in 1936.
Scientists have long debated the place of thylacines on the evolutionary tree of Dasyuromorphia, the order of carnivorous marsupials. Although they share many similar traits with canids, their last common ancestor existed 160 million years ago. The independent development of similar traits in these distantly related species suggests what's known as evolutionary convergence.
In the new study, researchers from Australia, Germany and the U.S. sequenced the thylacine genome by extracting DNA from a 108-year-old preserved thylacine pup stored at the Museum Victoria, in Melbourne, Australia. The researchers compared genomes from thylacines and other carnivorous marsupials, like the Tasmanian devil (Sarcophilus harrisii), with those of canids such as the red fox (Vulpes vulpes).
Beyond echoing previous research that thylacines are the oldest species in the order Dasyuromorphia, the study found that the shared characteristics of thylacines and canids are controlled by different genes. For instance, genes that control skull shape are not the same in both species, even though the skulls of thylacines and canids look quite similar.
The researchers propose that similarities between canids and thylacines arose because of other shared genetic influences, such as special regions of non-coding DNA called cis-regulatory elements that can control which genes get expressed. The team recommends that future research explore the contribution of non-coding DNA regions in instances of convergent evolution, to better explain this process.