The behaviour of B-chromosomes in meiosis was studied in 44 males of yellow- necked mouse, Apodemus flavicollis. The Bs behave in a non-Mendelian fashion during meiosis I i.e., appear as univalents, regardless of the number of Bs, and segregate in a random fashion. The meiotic drag of Bs, resulting from Bs lagging and premature division of Bs into chromatids, was found in 1B animals. The Bs drag amounts to about 6% of cells and is not substantial; however due to dispensable nature of Bs, it has to be compensated through drive in females or heterotic effects of Bs. This result gives support for the heterotic model of Bs evolution in A. flavicollis. On the other hand, the number of chiasmata on A-chromosomes showed increasing tendency with the number of Bs in the karyotype. As the chiasma effect is characteristic for parasitic Bs, it gives support for the parasitic model of Bs evolution. With contrasting results, the hypothesis of a combined model of Bs evolution, in which the fitness of B-bearers changes around the year or in different environmental conditions is discussed.
The current range and distribution of the common hamster, Cricetus cricetus in Poland was established. The range of the species has dwindled substantially in the course of just 30 years and the process is still going on. The Polish populations are isolated from the Belarussian, Czech and German ones, there is low probability of some exchange with Ukrainian hamsters. Moreover, two main areas of hamster distribution in Poland are isolated from each other. In view of the marked shrinkage and fragmentation of the range, we propose changing the status of this species in Poland from unknown (DD) to endangered (EN).
An isolated population of the common hamster, forming the western border of the species range in Poland was analysed by the use of 16 microsatellite loci and the mtDNA control region in two consecutive generations. The genetic diversity and the effective population size in this population are low. We found the evidence for ancient bottleneck in this population, but the results of tests for recent reduction of Ne were ambiguous. However, population functions properly i.e. it is in HW equilibrium, Fis and relatedness coefficients do not indicate inbreeding. It indicates that even isolated and small populations of the common hamster have good chance of survival on the condition of the protection and restoration of the habitats. Moreover, the sexrelated differences in dispersal in the common hamster were demonstrated through the relatedness analysis.
The common hamster (Cricetus cricetus L.) is supposed to be an abundant species in Eastern Europe including Ukraine. However, the current data on hamster’s occurrence in Ukraine from 1990 till nowadays show that the species became rare. The common hamster can be found in the West, North-East Ukraine and the Crimean peninsula. The species have declined in the forest-steppe zone and became extinct in most part of the steppe zone. Its actual distribution range has thus been strongly reduced. One of the possible causes of this decline is the habitat loss due to changes in agricultural management.
The existing literature, museum records, personal reports of field biologists and our own field results were compiled to assess the present distribution of the common hamster within Transylvania and the Pannonian Plain of Romania. Combining available distribution data and the existence of natural barriers we were able to designate five, possibly separate, populations: the Pannonian Plain, the Transylvanian Plateau, the Olt Valley, the Braşov Depression and the Ciuc Depression population. The Pannonian Plain and
the Transylvanian Plateau populations showed mass outbreaks in recent years. Twenty three individuals were available for the genetic analyses. The populations belonged to the Pannonia lineage, based on the sequences of 16SrRNA, cytb and ctr of mtDNA. In general we found very high diversity in mtDNA and 16 microsatellite loci. Moreover the most common ctr haplotypes for the Transylvanian Plateau were also present in the Pannonian Plain population and in populations from Hungary and Slovakia, which indicates recent or even current exchange of individuals. Summing up, recent mass outbreaks and high levels of genetic diversity, with some indication of current or very recent gene flow, showed that Romanian populations are in good state, at least compared to many other European countries. As such, these populations should be of particular interest and placed under protection, as they could serve as the reservoir of the genetic variability for the European Pannonia lineage of the common hamster.