Abstract
Betula humilis is an endangered plant species in Central Europe. In order to protect this species, it is necessary to document its genetic diversity in this region and to identify areas for conservation prioritisation. As molecular investigations conducted throughout the ranges of many plant species have shown that the highest genetic diversities are found within former glacial refugia and/or within the contact zones of different phylogenetic lineages, we investigated the reasons underlying the considerable genetic variation of B. humilis in northeastern Poland revealed previously using nuclear microsatellites. We analysed 365 individuals of B. humilis from 19 populations and 67 specimens of Betula pendula and Betula pubescens sampled in four geographical regions in Poland and Belarus for polymorphism in chloroplast PCR-restriction fragment length polymorphism markers. Genetic data strongly suggested that B. humilis could have survived the Last Glacial Maximum at higher latitudes, but the hypothesis of a refugium in southeastern Poland was rejected. Chloroplast DNA analysis confirmed high genetic diversity in some populations in northeastern Poland. This phenomenon can likely be explained in terms of a suture zone, as the high haplotypic richness was followed by h T ≤ v T. Similar patterns of haplotype distributions in the birches under study and high introgression ratio (IG = 0.71) among B. humilis and congeneric trees suggested that postglacial recolonisation of the shrub birch was complicated by haplotype sharing with other birches.
Highlights
Trees and shrubs of the genus Betula inhabit various ecosystems in temperate and boreal climate zones of the northern hemisphere
The aims of the present study were the following: (1) to quantify the chloroplast DNA (cpDNA) variation of B. humilis and its geographical distribution in Poland and Belarus and (2) to examine whether this variation confirms that northeastern Poland represents an area of high genetic diversity in this species, as was previously revealed using nuclear microsatellite analysis (Jadwiszczak et al 2011a)
Because the genetic variation of B. humilis can be influenced by hybridisation with congeneric species, we examined the pattern of cpDNA variation in the tree birches present in the same geographical regions and estimated the level of introgression between B. humilis and congeneric species in these regions
Summary
Trees and shrubs of the genus Betula inhabit various ecosystems in temperate and boreal climate zones of the northern hemisphere. In the history of the Holarctic region, birches appeared in the late Cretaceous (Środoń 1979). They are rare in early tertiary sediments, but in the late tertiary, birches were common and taxonomically diverse (Němejc 1975, cited in Środoń 1979). Four Betula species occur in Europe: Betula pendula Roth., Betula pubescens Ehrh., Betula nana L. and Betula humilis Schrk. Both palaeontological and genetic investigations have shown that B. pendula and B. pubescens could have survived the Last Glacial Maximum (LGM) in Southern European. The microthermal shrub B. nana could have existed in a periglacial belt during the last glaciation (Binney et al 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
