The Tasmanian tiger (Thylacinus cynocephalus), also known as the thylacine, was a carnivorous marsupial found throughout most of Tasmania before European settlement in 1803. The animal had tiger-like stripes running down its lower back and an abdominal pouch, but was perhaps best known for its wolf-like body. Despite sharing a last common ancestor 160 million years ago, the Tasmanian tiger and wolves independently evolved to look strikingly similar and had nearly identical skull shapes. A new study, published in the journal Genome Research, confirms that the resemblance between the Tasmanian tiger and the wolf isn’t just skin deep.
In 2018, Professor Andrew Pask from the University of Melbourne and Museums Victoria investigated links between the Tasmanian tiger and the wolf.
They sequenced the DNA of the Tasmanian tiger from a joey in order to probe their protein-coding DNA. However, their analysis of protein-coding genes revealed little evidence of molecular similarities.
In the new study, the team compared the rates of evolution across the genomes of 61 vertebrate species, leading to the discovery of hundreds of ‘non-coding’ DNA elements in the Tasmanian tiger and wolf.
“Non-coding regions of the genome were once considered ‘junk DNA’, but we now know that they play vital roles during development,” said Dr. Charles Feigin, a researcher at the University of Melbourne and Princeton University.
Non-coding DNA elements perform a distinct, but no less essential function to that of genes.
Rather than acting as a blueprint for proteins, these elements act as control regions that determine when, where and how much a given protein-coding gene is active.
Many of these elements showed signs of natural selection in both the Tasmanian tiger and wolf and were particularly common in DNA regions important for the development of the skull and brain.
“This was a surprising finding which reveals a lot about how animals evolve and sheds more light on the fascinating biology of the unique Tasmanian tiger marsupial,” Professor Pask said.
Charles Y. Feigin et al. Widespread cis-regulatory convergence between the extinct Tasmanian tiger and gray wolf. Genome Research, published online September 18, 2019; doi: 10.1101/gr.244251.118