The main goals of our study were to learn about the genetic diversity within the Tasmanian devils, and to present the results in ways that are potentially informative for efforts to conserve the species. We focused on single-nucleotide polymorphisms, traditionally abbreviated as "SNPs", which are positions in the genome where the members of the species contain different nucleotides (letters; A, C, G, or T). We determined the genome sequences of two individuals, as well as that from a DFTD tumor, and identified about 1 million SNPs. This number is low compared to other species where we have comparable data. For instance, two humans from Europe (or indeed from anywhere in the world) on average would have 3 or 4 times this number of nucleotide differences. We have made the SNPs and associated data available on the Galaxy web server; details about how to locate and use this information can be found by clicking on "Accessing Our Data" in the left panel.
It is widely held that low genetic diversity is associated with endangerment of a species. In the case of the Tasmanian devil, this may be especially true. The DFTD tumor arose in an animal that lived something like 20 years ago. The inability of other Tasmanian devils to reject the cell as coming from another individual may be related to lack of diversity in a genome region called the Major Histocompatability Complex, which in humans is associated with the rejection of grafts of tissue from another individual. However, low genetic diversity is only one factor behind species endangerment; another is the requirement for a very specific environment. Consider the following figure, which indicates one measurement of diversity, with endangered species indicated in red, and extinct ones shown in black. While pandas appear to have a high diversity, they are in danger for other reasons, such as their need for a very special diet. (Note that diversity in this figure is measured by the average number of SNPs in the mitochondrial sequence, excluding a hypervariable region, since it is only for this short sequence -- about 16,000 nucleotides -- that we have data for a large number of species.)