GEOGRAPHIC STRUCTURE OF CHLOROPLAST DNA POLYMORPHISMS IN EUROPEAN OAKS

Chloroplast DNA polymorphisms have been detected by the conventional S outhern-blotting hybridization method in four species of European oaks (Quercus petraea, Q. robur, Q. pubescens and Q. pyrenaica). Three pol ymorphisms, shared by at least three of these species, can be scored d irectly in ethidium bromide-stained gels and were used in a broad surv ey of the level of differentiation of the oak species and of their pat tern of genetic structure in western Europe. The highly significant ge ographic variation and the high genetic differentiation (Gst = 0.895, S(Gst) = 0.025) indicate a low level of cytoplasmic gene flow. We conc lude that cytoplasmic genomes are well suited for the reconstruction o f past migrational routes of such a complex of species.