I am interested in the construction of post-glacial small mammal communities and have studied the natural colonization history of European shrews, voles, mice and small carnivores, revealing a wide range of species- and lineage-specific responses in terms of source areas and pattern of spread. Unnatural colonization history (i.e. transport by humans) is also of interest to me, particularly the way that the phylogeography of small mammals transported by humans can inform about the history of the humans moving them. Those separate lineages that make up a species and which are formed in different places and colonize in different ways, are genetically differentiated to various degrees and may become separate species themselves. I am interested in the speciation process and the analysis of hybrid zones to inform about that. I have, in particular, studied the origin of chromosomally distinctive lineages, and the hybrid zones between those lineages, using shrews and mice as models.