Genetic diversity and sexual reproduction in relict populations of Betula nana

Abstract

In the present study, the impact of geographical isolation and habitat conditions on genetic diver-sity and sexual reproduction was tested in four relict populations of dwarf birch Betula nana L. in Poland and Belarus. Amplified fragment length polymorphism (AFLP) method revealed that the endangered central European stands were not genetically extirpated compared with the wide-spread localities from Finland and Russia, which can result from infrequent outcrossing events in long-living clonal populations. However, genetic clustering methods indicated significant differentiation of the Polish populations because of their small sizes and long-term geographical isolation. Considerable numbers of empty seeds were observed in both relict and central loca-tions, although fully developed seeds germinated better in widespread populations. Analysis of groundwater chemical parameters indicated that two relict populations were significantly differ-ent from the remaining samples with respect to pH, electrical conductivity and concentrations of phosphorus ions, which can also influence the efficiency of sexual reproduction. In the light of results obtained it seems that endangered B. nana localities are relatively stable.