The Greenland wolf
Having a ‘reference’ genome is a critical first step in genome analysis because it provides a basis against which other genetic data can be compared. A reference genome is a gold-standard, high-quality, DNA sequence of a species. Despite DNA sequencing being now relatively standardised, and relatively cheap, only 1.5 per cent of known complex organisms (including plants and animals) have had their genome sequenced. And that’s just the known species. If the estimated undiscovered species are added to the total, then only 0.1 per cent have had their genome sequence determined.
The Sanger Institute is currently leading work to sequence 70,000 species for the first time, as part of the Darwin Tree of Life Project in Britain and Ireland, and the global Earth BioGenome Project.
One of the genomes recently completed by Sanger researchers and their collaborators is the Greenland Wolf, Canis lupus orion, providing a new reference genome for research. This wolf is one of 38 subspecies of the grey wolf. Another sub species is Canis lupus familiaris – the domesticated dog.
There are thought to be just 200 Greenland wolves alive today, mainly living in their namesake country, with a smaller population on Ellesmere Island, Canada. They have a huge range, travelling far across their territories. They hunt arctic hares and muskoxen, and live in small packs of just a few animals.
Greenland wolf. Photo taken in Northern Greenland during an expedition funded by the Swedish Polar Research Secretariat. Credit: Love Dalén, Centre for Palaeogenetics.
The reference sequence of the Greenland wolf will be used by researchers such as paleogenomicist, Professor Greger Larson, Director Palaeogenomics & Bio-Archaeology Research at the University of Oxford. His work is uncovering stories of the ancient world.
“One of our main focuses is to understand the nature and to characterise the changing relationship between people and animals. And so we do that, not exclusively, but primarily by generating [genome] sequence data from the ancestors of modern populations.”
Larson uses DNA sequence data to create phylogenetic trees – similar to a family tree. The genetic similarities between individuals can be used to estimate relatedness. Population structures and lineages of species and sub-species can be mapped. Genome data give a much higher resolution view of evolutionary history than any other way of characterising a dog or a wolf.
What genome data can’t do is tell us about the relationship that an animal had with any other species – be that prey, or humans. This kind of information can be gathered from archaeological evidence though. For example, if a dog was buried in a grave, then researchers can start to infer something about the relationship between dogs and people at that time, in that place.
One of Professor Larson’s aims is to bring all this data together, and understand how it was that people and wolves first came together, how those wolves subsequently began to differ from their ancestors, and how wolves interacted with ancient human populations as the two species moved together all over the Earth.
“We try and plot that whole thing and actually watch the movie in real time,” he says.