Scots pine can serve as a case study for considering many aspects of gene flow. The reproductive biology of Scots pine is better known than that of most other conifers (Sarvas 1962, Koski 1970). The distribution of quantitative genetic variation of adaptive traits has been extensively studied, and for many important traits the populations are highly differentiated (Mikola 1982, Karhu et al. 1996, Hurme et al. 1997, Hurme and Savolainen in prep.). The distribution of variation in molecular markers has been well characterized. Until now, all markers, isozymes, RFLP, RAPD, microsatellites, have shown very limited degrees of differentiation. Thus, so far we have not found markers for those parts of the genome that are differentiated. At least many northern conifers may share similar patterns of biology (Savolainen and Kuittinen, in press). The basic findings of gene flow in Scots pine, through direct measures by marking pollen, paternity analysis and indirect genetic inference all suggest that gene flow through pollen is likely to be extensive.  The influence of timing of flowering in different populations is in the direction of facilitating south to north gene flow. There is strong selection for adaptation to local environmental conditions. The results of the contrasting influences of migration and selection  result in these divergent patterns of differentiation discussed above. These results can also be used for considering the consequences of fragmentation and management.

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