| Summary: | Many woodland plant species have huge distribution areas covering large parts of the Eurasian continent including areas that were glaciated during the last glacial period. In the present thesis, the geographic distribution of variation within such species is investigated and discussed in relation to glacial survival and post-glacial migration, dispersal ability, breeding system and levels of gene-flow between populations and related species, and various methods to measure and analyse genetic variation. The included studies concentrate on 1) the distribution of apomictic micro-species of Hieracium in the Nordic countries, 2) the distribution of allozyme variation throughout the Eurasian range of Carex digitata and Melica nutans, 3) the distribution of allozyme variation among closely related species of Carex sect. Digitatae, and 4) the distribution of allozyme variation in Milium effusum in two Swedish regions with contrasting history and geomorphology. It is concluded that: 1) Morphologically defined taxa within apomictic complexes may be useful tools when addressing phylogeographic questions. 2) Contrary to what has generally been assumed, levels of genetic variation are not always higher in unglaciated areas of southernmost Europe than in glaciated areas of northern Europe and there are several processes that may cause such patterns. 3) Geographically patchy distributions of genetic variation appear to be common in woodland plants and may be best explained by a leptokurtic mode of dispersal. 4) In both Carex digitata and Melica nutans, northern Europe appears to have been colonized through many independent long-distance dispersals from different extra-Fennoscandian populations, although these dispersals may have come mainly from the south in Carex digitata and mainly from the east in Melica nutans. 5) Although morphologically very similar, Carex pallens is genetically distinct from Carex digitata, whereas the morphologically and ecologically distinct Carex ornithopoda is not. Carex pediformis and C. humilis ...
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