%0 Research article
%T Population history, genetic variation and conservation status of the endangered birch species Betula nana L. in Poland
%A Jadwiszczak, Katarzyna A.
%A Drzymulska, Danuta
%A Banaszek, Agata
%A Jadwiszczak, Piotr
%D 2012
%J Silva Fennica
%V 46
%N 4
%R doi:10.14214/sf.905
%U https://silvafennica.fi/article/905
%X The effective conservation of species requires data on the levels and  distribution of genetic diversity within and among populations. In this  study, we estimated the genetic variation in three isolated populations  of Betula nana in Poland. An analysis of 11 nuclear microsatellites  revealed moderate mean heterozygosities (H<sub>O</sub>=0.556, H<sub>E</sub>=0.562),  low mean number of alleles per locus (A=4.57) and no inbreeding in the  total sample. An M-ratio test indicated that each population had  experienced a severe bottleneck in the past. Tests for heterozygosity  excess revealed that a significant decrease in the numbers of  individuals in two populations had occurred quite recently. The large  number of private alleles and very restricted number of migrants between  populations (Nm=0.35) strongly suggest that genetic drift and  geographic isolation are the primary factors responsible for the  reduction of genetic variation in the Polish populations of B. nana. We  detected two cpDNA haplotypes in the study populations, which can be  explained in terms of either the genetic drift acting on the relict  localities or a postglacial recolonisation from distinct refugia.  Palynological data indicated that one refugium could be located in the  Carpathians and their northern foreland. The primary threat to B. nana  in Poland is the overgrowth of its habitats by competing species, which  has likely resulted in a lack of generative reproduction in the mountain  populations.