Peter, B.M., and M. Slatkin. 2013. Detecting range expansions from genetic data. Evolution online early. doi: 10.1111/evo.12202.
We introduce a statistic ψ (the directionality index) that detects asymmetries in the two-dimensional allele frequency spectrum of pairs of population. These asymmetries are caused by the series of founder events that happen during an expansion and they arise because low frequency alleles tend to be lost during founder events, thus creating clines in the frequencies of surviving low-frequency alleles.
Bolfíková B., Konečný A., Pfäffle M., Skuballa J., Hulva P., 2013 Population biology of establishment in New Zealand hedgehogs inferred from genetic and historical data: conflict or compromise? Molecular Ecology 22: 3709–3720. doi: 10.1111/mec.12331.
One of the most problematic NZ invasions is that of the West European hedgehog (Erinaceus europaeus). A series of introductions from the United Kingdom last- ing until early in the 20th century has been dated to 1869 (Brockie 1990). Recently, this species has reached considerable population densities, even higher than in the native range in the case of the North Island (Brockie 1990).