The phylogeography and postglacial history of selected native European tree species

Previously, the postglacial history of plant taxa could only be inferred from fossil pollen data. With such palynological data, it was only possible to track the expansion of taxa from their glacial refugia in southern Europe over large geographical areas. No insight could be gained into expansion and colonisation over smaller areas.;Increasingly, modern molecular methods are being used to study all aspects of plant population genetics, including plant postglacial history. Here are reported studies into the postglacial history of five taxa of European forest tree using a molecular phylogeographical approach. Markers were generated using an effective PCR-RFLP approach. For Alnus glutinosa and Quercus petraea/robur, it is possible to deduce migration pathways not only over continental Europe taken by expanding refugial populations, but also over smaller geographical areas. Sympatric populations of Alnus cordata and A. glutinosa are shown to share chloroplast DNA haplotypes but to be distinct for nuclear DNA as determined by ISSR analysis. This is interpreted as being due to introgressive hybridization between these two alder species.;In the rowan, Sorbus aucuparia, a variable tandem repeat was found. The variation in this unusual mutation was used to try and deduce possible colonisation pathways. This proved to be difficult, as the location of possible refugial areas in this species are unknown. The final chapter describes the results of an investigation into levels of chloroplast DNA variation in Crataegus monogyna. This species is shown to have low levels of phylogeographically informative variation.