The Swedish Museum's specimen [NRM 566599] is an eviscerated adult female
preserved in ethanol. The specimen was acquired by Stockholm University
on the 30th April 1893 and transferred to the Swedish Museum of Natural
History in the early 1970s (ITSD, 2013). Before entering the university's
collection, the thylacine had been on display at the London Zoo from the
14th November 1884 until the 2nd April 1893. It had been snared at
Bowood (Tasmania) in August 1883 by Mr. A. W. Brewer, and was purchased
prior to its sale to the London Zoo by Dr. A. Bingham Crowther of Bridport
(Tasmania). The specimen is the finest preserved thylacine in existence.
The team extracted DNA from small samples of the hair of both specimens
and then sequenced independent copies of each region of the DNA molecule
from the many different fragments of DNA in the hairs. The high fidelity
of the team's results were assured by independently determining each position
in the sequences an average of 50 times.
The team sequenced all the DNA in the hair samples from the two thylacine
specimens, including mitochondrial DNA, which is the focus of the genome
research paper, and nuclear DNA, which the team plans to analyse in future
Schuster states: "This study, in which we sequenced the complete mitochondrial
genome of the thylacine species, also shows that it is feasible to sequence
its complete nuclear genome".
specimen 2 (GenBank accession number: FJ515781). Photo: International
Thylacine Specimen Database, 5th Revision 2013. Courtesy: Swedish
Museum of Natural History, (Stockholm).
The new gene sequences permitted the team to accurately determine how the
thylacine is related to other marsupials. In biology, the study of
how species are related is termed "phylogenetics"; hence the term "phylogenetic
tree". The team compared the sequences to a mitochondrial genome
sequence they determined from a living reference species; the numbat (Myrmecobius
The genome team state: "There has been an ongoing debate concerning
the precise position of the Tasmanian tiger within the marsupial family
tree. Early studies of bones and other morphological traits grouped
the thylacine with South
American carnivorous marsupials. Later morphological studies
placed it among Australian marsupials, possibly near the family Dasyuridae,
a group that includes the Tasmanian devil and quolls. The 1990's
saw the advent of the polymerase chain reaction and special methods for
recovering DNA from museum specimens. These early molecular studies
obtained only very short fragments of the thylacine's mitochondrial DNA
from museum specimens, but confirmed a close relationship near the devil
and its relatives, and a slightly more distant relationship to the numbat
(family Myrmecobidae). We have determined two thylacine mitochondrial
genomes, in addition to a modest fraction of the thylacine's nuclear genome.
These considerably longer DNA sequences now firmly place the thylacine
in the mammalian family tree, not as a close relative of the Tasmanian
devil, but separated by nearly 40 million years from the devil and the
Miller reports: "The two thylacine sequences were extremely similar
to each other, with only 5 differences in 15,492 nucleotides".
Nucleotides are the molecules that form the basic building blocks of RNA
and DNA. They are organic compounds composed of a nitrogenous base,
a sugar and a phosphate group. The similarity in the thylacine sequences
is indicative of a low level of genetic diversity within the species.
The genome team's research revealed that two
previous DNA sequences in public databases, both labelled as thylacine
mitochondrial genes, were incorrect. Schuster states: "Our Smithsonian
specimen was the male offspring of the female animal named as the source
of the earlier data, so the mitochondrial sequences, which are inherited
only from the mother, should have been identical, but our analyses showed
they are over 10 percent different".