Patterns And Causes Of Plant Genetic Diversity In  Northern Ecosystems

Outi Savolainen

Department of Biology
University of Oulu
PO Box 3000
FIN-90401 Oulu

The number of species is northern areas is much lower than in the south. Thus, genetic diversity may be an important component to the diversity. Genetic differentiation between populations can be generated through several different mecahnisms. Random drift  and founder effects combined with spatial isolation can be very effective, as will be demonstrated by  examining genetic variation in the molecular biology model organism Arabidopsis thaliana.

A special aspect of diversity in Scandinavia and the Nordic countries is the recent colonization of these areas after the Ice Age, which has left historical traces of the migration patterns. Some traces of the migration can be in the distribution of genetic variation in Norway spruce. The Russian and Scandinavian populations  of Arabidopsis lyrata (close outcrossing relative of Arabidopsis thaliana, plant molecular biology model organism) are highly differentiated with respect to isozymes, microsatellite variation, and sequence variation at Adh, presumably due to different post glacial sources and migration. On the other hand, variation in flowering time does not seem as divergent, as populations at the same latitude have evolved towards a similar optimum.

Natural selection can give rise to differential adaptation. Scots pine is known to locally adapted to different growing seasons at different latitudes.  This differentiation has occurred in the face of very strong migration, which causes most areas of the genome of Scots pine to be very similar across the distribution in Finland. The relevance of  such patterns of variation are discussed  also in the framework of forest management.