Abstracts (first author)
Glacial and postglacial history of Betula humilis in Poland and BelarusPDF
Trees and shrubs of the Betula genus inhabit diverse habitats in the Northern Hemisphere. In Europe, there are two tree birch species: Betula pendula and B. pubescens, and two shrub birches: B. nana and B. humilis. Both palaeontological and genetic investigations have shown that B. pendula and B. pubescens could have survived the Last Glacial Maximum (LGM) not only in southern European refugia but also at higher latitudes and after Holocene warming a rapid recolonisation occurred. The boreal shrub B. nana could have also existed in a periglacial area during the last glaciation. It is very difficult to reconstruct the glacial and postglacial history of B. humilis using solely palaeoecological data because the macrofossil record is rather scarce, and the pollen of this species is classified as B. nana type. The aim of the present study is to analyse variation of chloroplast DNA (cpDNA) haplotypes of B. humilis in order to describe the glacial and post-glacial history of the species in Poland and Belarus. Investigations were conducted in 25 populations of B. humilis. In total, 21 haplotypes were found but only two of them occurred with high frequencies. Clear predominance of two haplotypes in the studied area could be explained in terms of recolonisation from two distinct refugia. A weak genetic structure within the area populated by B. humilis has suggested that the species could have survived the LGM at higher latitudes. A glacial refugium of B. humilis was probably located in eastern Europe, another one could be situated in the Alps or the Carpathians. Low level of genetic diversity has not confirmed a hypothesis about B. humilis glacial isolate in south-eastern Poland. In turn, high haplotypic diversity has been revealed in some populations of B. humilis in north-eastern Poland and central Belarus. This pattern can likely be explained as a contact zone between different phylogeographic lineages.