Final Activity Report Summary - PHYLOMICROTUS (Phylogeography of the Orkney vole Microtus arvalis orcadensis)
This study represents a massive increase in our understanding of the genetics of the common vole Microtus arvalis; a total of 726 specimens were genetically typed. The reason why we studied this vole was to compare populations on the Scottish Orkney archipelago with those on continental Europe. Common voles are known to have been taken to Orkney from continental Europe by Neolithic people, so if it could be possible to establish the source area of the Orkney vole, that could help establish cultural links involving Neolithic people.
There is very little information on such cultural links and so voles could help increase our historical understanding. We used two types of genetic marker to address the colonisation of Orkney by voles. One type of genetic marker, mitochondrial DNA, showed a surprising result: the voles on Orkney did not genetically match with voles in continental Europe, even though we know that they derived from there. Also, the most likely source area (North France) showed less genetic variation than the island populations - the opposite from our expectations.
It appears what happened was that the French population of voles that colonised Orkney died out, and were much more recently replaced by another younger population, therefore with different genetic features and less genetic variation. For another type of genetic marker, microsatellites, there was a drop in genetic variation on Orkney compared with continental Europe, with smaller islands showing less variation, as expected. The data from this particular marker will allow us to date the timing of colonisation and establish how many colonists there were.
We already know from the substantial amount of mitochondrial DNA variation, that there were a large number of initial colonists on to Orkney. Therefore, in terms of using the Orkney vole as a proxy to understand the interaction between continental European and Orkney Neolithic people, unfortunately we could not find exactly where those Orkney-interacting continental people came from. We know that they did take a lot of voles with them, and we wonder if it may have been a deliberate introduction, may be for food.
In terms of evolutionary biology, our 'negative' results are important. They demonstrate clearly an example of one population characterised by one type of mitochondrial DNA replacing another population characterised by a different type of mitochondrial DNA. We suspect this relates to habitat change. When humans cleared woodland in continental Europe, there would have been a massive expansion of the grass-loving common vole. It is this expansion that probably led to the pattern that we discovered.
There is very little information on such cultural links and so voles could help increase our historical understanding. We used two types of genetic marker to address the colonisation of Orkney by voles. One type of genetic marker, mitochondrial DNA, showed a surprising result: the voles on Orkney did not genetically match with voles in continental Europe, even though we know that they derived from there. Also, the most likely source area (North France) showed less genetic variation than the island populations - the opposite from our expectations.
It appears what happened was that the French population of voles that colonised Orkney died out, and were much more recently replaced by another younger population, therefore with different genetic features and less genetic variation. For another type of genetic marker, microsatellites, there was a drop in genetic variation on Orkney compared with continental Europe, with smaller islands showing less variation, as expected. The data from this particular marker will allow us to date the timing of colonisation and establish how many colonists there were.
We already know from the substantial amount of mitochondrial DNA variation, that there were a large number of initial colonists on to Orkney. Therefore, in terms of using the Orkney vole as a proxy to understand the interaction between continental European and Orkney Neolithic people, unfortunately we could not find exactly where those Orkney-interacting continental people came from. We know that they did take a lot of voles with them, and we wonder if it may have been a deliberate introduction, may be for food.
In terms of evolutionary biology, our 'negative' results are important. They demonstrate clearly an example of one population characterised by one type of mitochondrial DNA replacing another population characterised by a different type of mitochondrial DNA. We suspect this relates to habitat change. When humans cleared woodland in continental Europe, there would have been a massive expansion of the grass-loving common vole. It is this expansion that probably led to the pattern that we discovered.