Correct identification of the source population of an invasive species is a prerequisite for testing hypotheses concerning the factors responsible for biological invasions. The native area of an invasive species may be large, poorly known and/or genetically structured. As a consequence, studies based on molecular markers are likely to generate incorrect conclusions about the origin of introduced populations. We recently evaluated and quantified this risk by performing analyses on simulated microsatellite data sets. On the basis of the obtained results, we then developed a new methodology within an Approximate Bayesian Computation framework* which substantially reduces the risk of wrong inferences. Finally, this method was successfully applied to the invasive Asian ladybird Harmonia axyridis. We found that the invasive population in eastern North America, which has served as the bridgehead for worldwide invasion by H. axyridis, was probably formed by an admixture between two native Asian populations. This admixture may have facilitated adaptation of the bridgehead population.
*Approximate Bayesian Computation: class of computational methods rooted in Bayesian statistics in which data are replaced by summary statistics and the likelihood is approximated by the use of a simulation model.
- Lombaert, E., T. Guillemaud, C. E. Thomas, L. J. L. Handley, J. Li, S. Wang, H. Pang, I. Goryacheva, I. A. Zakharov, E. Jousselin, R. L. Poland, A. Migeon, J. van Lenteren, P. De Clercq, N. Berkvens, W. Jones, and A. Estoup. (2011) Inferring the origin of populations introduced from a genetically structured native range by approximate Bayesian computation: case study of the invasive ladybird Harmoniaaxyridis.Molecular Ecology20:4654-4670.