Genetic diversity reduction after translocation in animals

Schematic of translocation of a part (in red) of the population (in blue) across a barrier. In reality, the part of the population moved will be a very small subset. In animals, perhaps as low as a few individuals

What did we do?

We scanned the literature for studies of introduced populations of which there is no record that they were re-stocked and for which there is no record that the population of origin ever reached the translocated population. Typical examples are vertebrates animals released on islands, or in regions far from their native region. Furthermore, the founder size had to be known. Lastly, the research had to contain information on the loss of genetic diversity (heterozygosity and allelic richness) of the founded population and the population of origin.

Our working hypothesis was that smaller size of the translocated population reduced genetic diversity, which indeed was clear for allelic richness. We furthermore expected that translocated populations that showed a marked population growth rate after founding had managed to retained higher diversity, because they would have been able to quickly achieve a sufficiently large effective population size. Nevertheless, we did not find evidence for this hypothesis in the review of the studies.

Overall, there were few studies adhering to this stringent criteria we had set up in order to investigate what the population genetic consequences of translocation are in animals. There are many translocations out there and we conclude that before conservation biologists start to apply approaches such as assistsed colonisation, increased effort in evaluating the consequences of past translocations (which are typically poorly documented) are needed. 


Jon Brommer