Post-glacial colonization, drift, local selection and conservation value of populations: a northern perspective

Many boreal species have wide geographical distribution, the populations are evolutionarily young, and the species diversity generally decreases with the latitude. Therefore the intraspecific genetic diversity gets a high relative value as an important component of biodiversity. We review here the observed patterns of genetic differentiation in boreal populations, mainly in northern Europe. The observed patterns of differentiation call result from different colonization histories, genetic drift associated to restricted dispersal, clonal reproduction and demographic fluctuation, and finally adaptation to the steep environmental gradients at northern latitudes. This means that the populations form both evolutionarily and demographically separate units, and this genetic differentiation should be taken into account in any conservation plans aiming to preserve existing biodiversity. We also evaluate the applicability of the concepts ESU (evolutionarily significant unit) and MU (management unit) in these situations.