Department of Computational Biology, University of Lausanne, Lausanne, Switzerland.|Centre for Geogenetics, University of Copenhagen, Copenhagen, Denmark.|Department of Computational Biology, University of Lausanne, Lausanne, Switzerland.|Centre for Geogenetics, University of Copenhagen, Copenhagen, Denmark.|The Bioinformatics Centre, Department of Biology, University of Copenhagen, Copenhagen, Denmark.|Department of Statistics, University of California, Berkeley, CA, USA.|Department of Computational Biology, University of Lausanne, Lausanne, Switzerland.