Aneuploids in the shrub birch Betula humilis populations in Poland

Shrub birch (Betula humilis Schrk.) is endangered glacial relict growing in natural and drained fens and transitional mires. At present study we examined karyotypes of 103 individuals of B. humilis, collected in six populations from eastern and northeastern Poland. We found 60% of diploid individuals with 2n = 28. The rest of studied plants were aneuploids with 26, 27, 29, 30 and 31 chromosomes in their karyotypes. High frequencies of aneuploids in Polish populations of B. humilis could be a consequence of: (i) hybridization with congeneric species, (ii) stress resulting from range fragmentation, (iii) karyotype instability of individuals with 2n ≠ 28, or (iv) vegetative reproduction

Identification of the barrier to gene flow between phylogeographic lineages of the common hamster Cricetus cricetus

In anthropogenically disturbed habitats, natural barriers still exist and have to be recognized, as they are important for conservation measures. Areas of phylogeographic breaks within a species are often stabilized in inhospitable regions which act as natural barriers. An area of contact between phylogeographic lineages of the common hamster (Cricetus cricetus) was found in the Małopolska Upland in Poland. A total of 142 common hamsters were captured between 2005 and 2009. All hamsters were genotyped at 17 microsatellite loci and partial sequences of the mitochondrial (mtDNA) control region were obtained. No mixed populations with mtDNA haplotypes of both lineages were found. The distance between marginal populations was about 20 km; no hamsters were found in the area between. A principal components analysis (PCA) was performed on microsatellite data and the greatest change in PC1 scores was found between marginal samples. To define the habitat components responsible for the phylogeographic break, we compared the habitat composition of sites occupied by hamsters with those from which hamsters were absent. We found that hamsters avoided forested areas and sandy soils. The area of the potential barrier was characterized by a high proportion of woodland and unfavorable soils in comparison with neighboring areas inhabited by hamsters. They cannot settle in this area due to their high winter mortality in shallow burrows and high predation in the fields adjacent to forests

The history of species reacting with range shifts to the oceanic-continental climate gradient in Europe. The case of the common hamster (Cricetus Cricetus L.)

Zmiany zasięgu występowania gatunków zależne są w dużej mierze od zmieniającego się cyklicznie klimatu. W przeszłości glacjały oraz interglacjały niejednokrotnie doprowadzały do zwiększenia lub utraty zajmowanego przez taksony obszaru. Niekorzystny dla siebie okres czasu gatunki mogły przetrwać w miejscach określanych jako refugia. Lokalizacja obszarów refugialnych mogła być różna, w zależności od tolerancji klimatycznych oraz wymagań środowiskowych organizmów. Dotychczasowe analizy bio- i filogeograficzne gatunków europejskich brały pod uwagę tylko jeden, równoleżnikowy gradient klimatyczny, czyli zmiany temperatury przebiegające z północy na południe. Jednak, w przypadku niektórych gatunków istotnym czynnikiem wpływającym na ich rozmieszczenie jest gradient klimatyczny oceaniczno - kontynentalny, który w Europie jest południkowy. Przykładem takiego gatunku jest chomik europejski (Cricetus cricetus), który w ostatnich latach utracił znaczną część swojego zasięgu występowania w Europie Zachodniej i Centralnej. Przyczyn tak gwałtownego spadku liczebności populacji i zmniejszenia zasięgu doszukiwano się w intensyfikacji rolnictwa i urbanizacji terenów dotychczas rolniczych. Niemniej jednak istotnym czynnikiem mogą być także, pomijane dotychczas wpływy klimatu i przesunięcie się gradientu klimatycznego oceanicznego w kierunku wschodnim.Species 'range shifts' oscillated in response to cyclical climate changes. Glacial and interglacial cycles in the past often led to increase or contraction of the taxa range. The places where species persist during the period of the species' maximum contraction in range have been described as refuges. The location of refuges' areas depends mainly on the climate adaptation and environmental tolerance of individual species. Most of the bio- and phylogeographic studies performed so far in Europe recognized only one climatic gradient, which is latitudinal (important factor is temperature decreasing northwards). The other climatic gradient, that is often ignored in phylogeographic research, is the oceanic - continental one that in Europe is longitudinal. The common hamster (Cricetus cricetus) is the species adapted to continental climate which has lost large parts of its previous range in Western and Central Europe. The causes for this decline are not clearly understood but the main reasons taken under consideration are the changes occuring in agricultural management and urbanization of formerly agricultural areas. However, current shrinkage of the range may also be a response to oceanic climate gradient extending eastwards in Europe

Genetic diversity and sexual reproduction in relict populations of Betula nana

In the present study, the impact of geographical isolation and habitat conditions on genetic diversity and sexual reproduction was tested in four relict populations of dwarf birch 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 widespread 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 locations, although fully developed seeds germinated better in widespread populations. Analysis of groundwater chemical parameters indicated that two relict populations were significantly different 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 localities are relatively stable.Betula nanaB. nan

The genetic characterization of an isolated remnant population of an endangered rodent (Cricetus cricetus L.) using comparative data: implications for conservation

Estimates of genetic diversity and phylogenetic affiliation represent an important resource for biodiversity assessment and a valuable guide to conservation and management. We have found a new population (Jawor—JW) of the common hamster Cricetus cricetus in western Poland that is remote from the nearest populations by 235–300 km. With the objective of genetically characterizing of this population, we compared it with other populations from Poland and Germany by taking into account sequences of four mitochondrial DNA genes and variation at 10 microsatellite loci. The JW population exhibited low levels of genetic diversity and allelic and haplotype richness, which likely reflects its extreme isolation. This factor, coupled with inbreeding and genetic drift, are major threats to JW. A neighbor-joining tree based on mtDNA haplotypes shows that JW clusters among samples representing the Central subgroup that is known from central Germany but that has not yet been identified in Poland. Findings presented here improve our understanding of the spread and diversification of the common hamster. We offer the following hypotheses to explain the observed pattern of mtDNA haplotype distribution: JW could be a byproduct of postglacial migrations or back-migrations from eastern refugia to the western part of Europe, or/and be a result of population and habitat fragmentation. We recommend translocation of individuals as an effective management strategy, both at the level of Central phylogeographic group and at the species level, to overcome the negative consequences of inbreeding and geographical isolation of the JW population