Cricetus Research Articles

Low genetic diversity and significant structuring of the common hamster populations Cricetus cricetus in Poland revealed by the mtDNA control region sequence variation

The genetic diversity of 12 populations in the present range of the common hamster Cricetus cricetus (Linnaeus, 1758) in Poland was established. The 366 bp of the mtDNA control region was sequenced for 195 individuals. As few as seven haplotypes were found and their distribution was geographically structured. The large geographic areas were fixed or almost fixed for a single haplotype and three groups of populations, that do not share any haplotypes, have been defined. Proportions of genetic diversity attributable to variation between groups of populations, between populations within groups and within populations were 93.64, 1.92 and 4.45% (SAMOVA: p < 0.001 for all estimates), respectively. Such pattern of variation is most probably the result of historical, postglacial bottlenecks and present genetic drift after the population decline in the last few decades.

Circannual Phase Response Curves to Short and Long Photoperiod in the European Hamster

This study investigated in male European hamsters (Cricetus cricetus ) whether entrainment of circannual rhythms follows the principles of the nonparametric entrainment model. In 2 experiments the times of the year when long (LP) or short photoperiod (SP) are able to synchronize the reproductive cycle were determined, by recording phase response curves (PRCs). A total of 28 groups of 10 hamsters were synchronized by SP, before being subjected to 2 converse experiments: a) 14 groups were transferred to constant LP, only interrupted by SP for 1 month (SP-pulse), the pulse being increasingly delayed between groups by 2 weeks or 1 month steps; and b) the remaining 14 groups stayed in constant SP interrupted by LP for 1 month (LP-pulse) at different phases of the cycle. In a 3rd experiment 5 groups of 10 European hamsters were subjected to constant LP interrupted by 1-month SP-pulses in regular non-365-day zeitgeber intervals (circannual T-cycles) differing between groups (c). The reproductive state was checked every 2 or 4 weeks. The PRCs revealed that an SP-pulse had a very strong phase-resetting capability of -180 degrees to at least +81 degrees in subjective summer (a). During subjective winter when the animals hibernate, a SP-pulse had only weak effectiveness (a) whereas an LP-pulse advanced the circannual clock by up to +41 degrees (b). In the latter conditions a further advance of up to +156 degrees was achieved by the decrease in photoperiod at the return to SP conditions, which terminated the reproductive phase already after 4 to 5 weeks. In different circannual T-cycles the animals entrained for at least 2 cycles (c). In conclusion, 1) the circannual rhythm of European hamsters can be entrained by one photoperiodic signal per cycle, 2) the decrease in photoperiod is most important for its synchronization, and 3) as in circadian clocks the resetting of circannual clocks follows the principles of the nonparametric entrainment model.

Population structure, colonization processes and barriers for dispersal in Polish common hamsters (Cricetus cricetus)

The phylogeographic relationships of common hamster (Cricetus cricetus) populations in Poland were determined by the analysis of three partial mtDNA sequences: control region, cytochrome b and 16S rRNA. A phylogenetic tree as well as parsimony network, consistently separate Polish common hamsters into two groups: E1 being so far specific for the area of Poland, and P3 which clusters inside a Pannonian lineage, previously described from the Carpathian Basin. Polish hamsters do not share any haplotypes with the ‘North’– lineage from Germany and Western Europe, although Poland most likely represents the main migration corridor from the eastern distribution centre to the western boundary of the species range. Fossil and DNA data indicate a very recent appearance of the E1 lineage in the Polish Uplands, probably at the very end of the last glaciation. On the other hand, the Pannonian group entered southern Poland as early as the second stadial of the last glaciation (Middle Vistulian 53.35 ka). The hamster lineages in Poland seem to show different population structures and demographic histories. Die phylogeographische Beziehung rezenter Populationen des Feldhamsters (Cricetus cricetus) in Polen wurde anhand der Haplotypenverteilung von drei partiellen mitochondrialen Genen (Kontrollregion, Cytochrom b und 16S rRNA) untersucht. Genetische Stammbäume und Netzwerke zeigen, dass polnische Feldhamster in zwei phylogenetische Linien aufspalten, E1 und P3. Die E1-Linie ist bisher nur für Polen bekannt, während die P3-Gruppe zur pannonischen Linie gehört, die bisher nur für das Karpatenbecken beschrieben ist. Polnische Feldhamster teilen keine mitochondrialen Haplotypen mit der ‘North’-Linie in Deutschland und Westeuropa, obwohl Polen als wahrscheinlicher Besiedlungskorridor vom östlichen Verbreitungsschwerpunkt in das westliche Areal infrage kommt. Fossildaten und DNA-Analysen weisen auf eine späte Besiedlung Polens durch die E1-Linie hin, die wahrscheinlich gegen Ende der letzten Eiszeit erfolgte. Im Gegensatz dazu erreichte die pannonische Gruppe Südpolen im zweiten Stadial der Weichseleiszeit. Die beiden Feldhamsterlinien in Polen haben nicht nur verschiedene Populationsstrukturen, sondern auch unterschiedliche demographische Hintergründe. Data s1. Population structure, colonization processes and barriers for dispersal in polish common hamsters (Cricetus Cricetus). Please note: Wiley-Blackwell are not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Morphometric Differences Between the Phylogeographic Lineages of the Common Hamster Cricetus Cricetus in Poland

Morphometric Differences Between the Phylogeographic Lineages of the Common Hamster Cricetus Cricetus in Poland As the common hamster is endangered in the European part of its range, it is necessary to define the conservation units for successful management of natural populations. Here we describe the case of clear morphometric differentiation between phylogeographic lineages of the common hamster. The standard external measurements were taken from 209 common hamsters collected during the period 2005-2007 from the present species range in Poland. The studied populations belong to different phylogeographic lineages P3 (Polish Pannonia) and E1, and the hamsters of P3 lineage are smaller with longer feet and tails than the hamsters of E1 lineage. The phylogeographic lineages of the common hamster can be defined as evolutionary significant units (ESU) due to the significant genetic differentiation and as management units (MU) with the evidence for ecological differentiation.

The behaviour of the common hamster ( Cricetus cricetus) under zoo conditions

Studies on the behaviour of the common hamster are very rare and fragmentary. From August till the middle of September 2005 we observed behaviour of six individuals of the common hamster (one female and five juveniles: three males and two females) and from the second part of September till October 2005 we observed behaviour of two juvenile males after they were separated from the group. The “Focal animal sampling” was used as an observation method, and the total time of observation amounted to 75 hours. During our observation 7707 bouts of behaviour were recorded. Both social and non-social behaviour were categorised. The number of the non-social behaviour prevailed significantly over the number of the social behaviour (n=496; 6.4%). The most frequent observed non-social behaviour was: head rearing (n=2019; 28%). Among interindividual interactions “escape” (45.4%; n=225) and “vocalisation” (15.7%; n=78) were noticed most frequently. Play-fighting, direct identification, following and hugging were the only aspects of the social behaviour characteristic of the young. The behaviour repertoire of the common hamster seems to be similar to the behaviour of the golden hamster ( Mesocricetus auratus).

Shedding light on the hidden costs of the Habitats Directive: the case of hamster conservation in Germany

The EU Habitats Directive provides in Annexes II and IV a list of species that need to be conserved. In response to this obligation, Member States have implemented a variety of conservation measures. These measures include the rejection, modification or delay of land development plans, payments to landowners for implementing conservation measures and management actions such as breeding programmes. The extent of the cost of these various conservation measures is not always apparent. Particularly when land development plans are modified costs are hidden because there is no visible flow of financial resources. This may lead to an underestimation of conservation costs. In contrast, costs which directly lead to a flow of financial resources, such as expenses for management measures, are visible and may be given more attention. This difference in visibility may result in selecting conservation measures with high but hidden costs, whereas conservation measures with low but visible costs are neglected. The first purpose of this paper is to provide a framework that captures, along with the visible costs, the range of hidden costs relevant to the conservation of species protected by the Habitats Directive. The second purpose is to demonstrate the relevance of the problem of hidden costs by means of a case study. We apply the framework to estimate the costs of protecting the common hamster (Cricetus cricetus, listed in Annex IV of the Habitats Directive) in the region of Mannheim, Germany and find that the hidden costs of changes in development plans are higher than the visible conservation costs by at least an order of magnitude.

Reproductive performance in female common hamsters

We monitored individual reproductive timing and output in a common hamster population in Vienna over a 3-year period. Animals were live-trapped, weighed, individually marked, and reproductive status was determined at capture. Costs of reproduction were investigated by measuring body condition shortly before hibernation and overwinter survival. Our results indicated that early emerging females had more litters and weaned more offspring per season. Body mass throughout the active season did not differ significantly between females with high and low reproductive output. High reproductive output seemed to affect the duration of the active season. Successful females had a longer postreproduction period before hibernation than less successful ones, probably serving to balance the costs of reproductive effort by extended preparation for hibernation. Also, females that had emerged early in spring and had high reproductive success were more likely to survive the subsequent winter. Hence, we found female common hamsters to vary strongly in maternal investment capacity and to tailor reproductive strategies accordingly.

The circadian clock stops ticking during deep hibernation in the European hamster.

Hibernation is a fascinating, yet enigmatic, physiological phenomenon during which body temperature and metabolism are reduced to save energy. During the harsh season, this strategy allows substantial energy saving by reducing body temperature and metabolism. Accordingly, biological processes are considerably slowed down and reduced to a minimum. However, the persistence of a temperature-compensated, functional biological clock in hibernating mammals has long been debated. Here, we show that the master circadian clock no longer displays 24-h molecular oscillations in hibernating European hamsters. The clock genes Per1, Per2, and Bmal1 and the clock-controlled gene arginine vasopressin were constantly expressed in the suprachiasmatic nucleus during deep torpor, as assessed by radioactive in situ hybridization. Finally, the melatonin rhythm-generating enzyme, arylalkylamine N-acetyltransferase, whose rhythmic expression in the pineal gland is controlled by the master circadian clock, no longer exhibits day/night changes of expression but constantly elevated mRNA levels over 24 h. Overall, these data provide strong evidence that in the European hamster the molecular circadian clock is arrested during hibernation and stops delivering rhythmic output signals.

Seasonal variations of clock gene expression in the suprachiasmatic nuclei and pars tuberalis of the European hamster (Cricetus cricetus)

In mammals, day length (photoperiod) is read and encoded in the main circadian clock, the suprachiasmatic nuclei (SCN). In turn, the SCN control the seasonal rhythmicity of various physiological processes, in particular the secretion pattern of the pineal hormone melatonin. This hormone then operates as an essential mediator for the control of seasonal physiological functions on some tissues, especially the pars tuberalis (PT). In the European hamster, both hormonal (melatonin) and behavioral (locomotor activity) rhythms are strongly affected by season, making this species an interesting model to investigate the impact of the seasonal variations of the environment. The direct (on SCN) and indirect (via melatonin on PT) effect of natural short and long photoperiod was investigated on the daily expression of clock genes, these being expressed in both tissues. In the SCN, photoperiod altered the expression of all clock genes studied. In short photoperiod, whereas Clock mRNA levels were reduced, Bmal1 expression became arrhythmic, probably resulting in the observed dramatic reduction in the rhythm of Avp expression. In the PT, Per1 and Rev-erbalpha expressions were anchored to dawn in both photoperiods. The daily profiles of Cry1 mRNA were not concordant with the daily variations in plasma melatonin although we confirmed that Cry1 expression is regulated by an acute melatonin injection in the hamster PT. The putative role of such seasonal-dependent changes in clock gene expression on the control of seasonal functions is discussed.

Seasonal changes in cortisol and progesterone secretion in Common hamsters

In this study, we investigated endocrine factors and behaviour in free-living Common hamsters ( Cricetus cricetus) during reproductive and non-reproductive periods of the annual cycle. We applied a non-invasive method to gain information on seasonal changes in adrenocortical activity in male and female hamsters by analysing faecal glucocorticoid metabolite concentrations (FCM). In addition, plasma progesterone concentrations were monitored in females throughout the non-hibernation season. The animals were live-trapped from spring emergence until the onset of hibernation in autumn. Reproductive status was determined at capture and blood and faecal samples were collected. During behavioural observations, agonistic and sexual interactions were recorded. FCM concentrations were significantly higher in males than in females during the reproductive period. In males, a pronounced increase in FCM during the reproductive period coincided with high frequencies of intrasexual aggression. In females, FCM levels remained relatively constant. Aggressive behaviour in females increased during the reproductive period, but was much less frequent than in males. Females, which successfully raised a second litter after a postpartum oestrus and concurrent lactation and gestation had lower FCM levels than individuals, which lost their second litter after parturition. As expected, plasma progesterone concentrations were low before and after the reproductive period. During gestation, levels peaked and remained elevated during lactation. The results of this field study provide insight in critical periods associated with reproduction in male and female Common hamsters.

Rapid and reversible changes in intrahippocampal connectivity during the course of hibernation in European hamsters

The hippocampal formation is a highly plastic brain structure that undergoes structural remodeling in response to internal and external challenges such as metabolic imbalance and repeated stress. We investigated whether the extreme alterations in metabolic status that occur during the course of hibernation in European hamsters cause structural changes in the dendritic arborizations of the CA3 pyramidal neurons and their main excitatory afferents, the mossy fiber terminals (MFT), that originate in the dentate gyrus. We report that apical, but not basal, dendritic trees of Golgi-impregnated CA3 principal neurons are significantly shorter, less branched, and less spiny in hypothermic hamsters compared with active animals. After the induction of arousal from torpor, within 2 h, the apical dendritic lengths, branching patterns, and spine density estimations returned to levels found in active, euthermic hamsters. The ultrastructure of MFT in hibernating hamsters showed a significant reduction in synaptic vesicle density and in the percentage of MFT area covered by spine profiles. Awakened hamsters showed restoration of MFT morphology to that seen in active animals. MFT of torpid animals also showed a significant increase in the percentage area of mitochondrial profiles that remained higher 3 h after induced arousal from hibernation compared with euthermic controls. Thus, the torpid/awakening cycle of the hibernating European hamster causes a rapid and reversible morphological reorganization of intrahippocampal subregions involved in information processing. The reported reductions in morphological connectivity between the dentate gyrus and the CA3 subregions could underlie the cessation of exploratory activity and spatial navigation skills during hibernation.

Asymmetric Control of Short Day Response in European Hamsters

The European hamster (Cricetus cricetus) is a circannual species in which the synchronization of the circannual cycle to the natural year occurs during 2 annual phases of sensitivity. Around the summer solstice, the animals are sensitive to a shortening of photoperiod. During this sensitive phase, pronounced changes in circadian output parameters are observed, indicating a different functional state of the circadian system. This special state is assumed to be necessary to develop the extreme sensitivity to short day length in European hamsters during this phase. In natural conditions, the animals are able to recognize the shortening of photoperiod already in mid-July, when the photoperiod is reduced only by 30 min. To investigate the short-day response in sensitive European hamsters on the basis of the 2-coupled oscillator model of Pittendrigh and Daan (1976), daily activity and the reproductive state of European hamsters were recorded after an asymmetrical reduction of photoperiod from long (LD 16:08) to short (LD 08:16) photoperiods. The activity pattern of the animals showed an immediate response to the short photoperiod at the day of transfer when the night was extended only into the evening, but there was a significant delay in the response time when the night was extended into the morning. Thus, the evening oscillator E is more important in inducing the photoperiodic response than the morning oscillator M. Moreover, the broad intragroup variation in the latter conditions strongly suggests that the changes in the activity pattern were endogenously induced and that the animals were not able to recognize a lengthening of the night into the morning. Gonadal regression started in both groups 3 weeks after the change in the activity pattern, indicating that this process is initiated when the circadian system has received the short-day signal either through changes in photoperiod or through the circannual clock.

Eight new polymorphic microsatellite loci for genetic analyses in the endangered common hamster (Cricetus cricetus L.)

AbstractWe developed primers for eight polymorphic microsatellite loci in the endangered common hamster (Cricetus cricetus L.). Population genetic parameters were analysed on the basis of 70 adult individuals captured from a single population. Allele numbers per locus ranged from eight to 17. Expected and observed heterozygosities per locus ranged from 0.67 to 0.91 and from 0.41 to 0.8, respectively.

Genetic spatial structure of European common hamsters (Cricetus cricetus) — a result of repeated range expansion and demographic bottlenecks

The spatial genetic structure of common hamsters (Cricetus cricetus) was investigated using three partial mitochondrial (mt) genes and 11 nuclear microsatellite loci. All marker systems revealed significant population differentiation across Europe. Hamsters in central and western Europe belong largely to two allopatric mitochondrial lineages south and northwest of the Carpathian and Sudetes. The southern group, 'Pannonia', comprises populations inside the Carpathian basin (Czech Republic, Hungary) while the second group, 'North', includes hamsters from Belgium, the Netherlands, France, and Germany. Isolation of the lineages is maintained by a combination of geographical and ecological barriers. Both main phylogeographical groups show signs of further subdivision. North is separated into highly polymorphic central German and less polymorphic western populations, which most likely split during late glacial expansion (15,000-10,000 bp). Clock estimates based on haplotype distributions predict a divergence of the two major lineages 85,000-147,000 bp. Expansion times fall during the last glaciation (115,000-10,000 bp) corroborating fossil data, which identify Cricetus cricetus as characteristic of colder climatic phases. Despite the allopatry of mt haplotypes, there is an overlap of nuclear microsatellite alleles between phylogeographical units. Although there are strong evidence that Pannonian hamsters have persisted inside the Carpathian basin over the last 50,000 years, genetic differentiation among European hamsters has mainly been caused by immigration from different eastern refugia. Possible source populations are likely to be found in the Ukrainian and the southern Russian plains--core areas of hamster distribution. From there, hamsters have repeatedly expanded during the Quaternary.

Seasonal variations in circadian rhythms coincide with a phase of sensitivity to short photoperiods in the European hamster

European hamsters (Cricetus cricetus) show pronounced seasonal changes in their physiology and behavior. The present study provides a detailed analysis of the temporal relationship between seasonal cycles of reproduction and body mass and seasonal changes of two circadian parameters, i.e., locomotor activity and 6-sulphatoxymelatonin (aMT6s) excretion, in individual animals kept under natural light conditions. Our results demonstrate a characteristic pattern of locomotor activity and aMT6s excretion observed around the summer solstice, i.e., from mid-May to mid-July. During this time, locomotor activity was characterized by a high level of activity and an early activity onset, while the nightly elevation of melatonin was reduced to baseline levels. These seasonal changes in aMT6s excretion and locomotor activity were only loosely related to changes in the reproductive status of the animals, but correlated well with a period of the annual cycle during which the animals were sensitive to short days. They may therefore reflect a specific state of the circadian pacemaker system within the SCN and can thus be a valuable tool to further characterize molecular and physiological mechanisms of photoperiodic time measurements in European hamsters.

The Organ Blood Flow under Conditions of Motor Rest in Rodents with Different Body Mass

The volume velocity of organ blood flow (VVBF) was measured using 86RbCl in anesthetized wild rodents (birch mouse, narrow-skulled vole, and common hamster) as well as in wakeful and anesthetized Wistar rats and Balb mice. It has been shown that with increase of the rodent body mass (from 8 g to 760 g) and decrease of the specific minute volume of blood circulation (VVBF/100 g organ), VVBF is unchanged in kidney, decreases, although to a lesser extent than cardiac output (CO), in digestive tract, liver, spleen, and heart, whereas in supporting-motor and covering structures it decreases to a greater extent than CO.

Body temperature and above‐ground patterns during hibernation in European hamsters (Cricetus cricetus L.)

AbstractThe purpose of this study was to determine whether hibernating European hamsters Cricetus cricetus, L., 1758 stay in their burrows all winter or if they occasionally spent time above ground. If ‘time (spent) above ground’ (TAG) occurred regularly throughout hibernation, the second objective of this work was to categorize and quantify the patterns of TAG during winter. For this purpose, 11 European hamsters were individually housed in wire mesh cages that were buried in the ground of an outdoor enclosure. Each cage was filled with soil up to ground level allowing the animals to construct their own burrows within the cages. Antennae in the bottom and top of the cage were calibrated to receive signals only when the hamsters were in their burrows or above the ground, respectively. This method enabled continuous recordings of the animal's TAG and provided ecologically meaningful results as the animals were housed in a way that closely resembled their natural habitat. About half of the hamsters stayed continuously below ground. Of these hamsters, almost all showed a dense pattern of episodes of reduced body temperature separated by only brief periods of normothermia. In contrast, the other half of the animals moved either episodically or even regularly above ground. For all of these hamsters, TAG was significantly reduced as compared to normothermic values. One hamster did not show any hibernation but did have a significantly reduced normothermic body temperature and did not leave its burrow for periods of up to 3 weeks.

A risk analysis for the common hamster ( Cricetus cricetus)

The common hamster ( Cricetus cricetus) has suffered a dramatic decline in Western Europe though the species is characterized by an extremely high reproductive potential. An individual-based model was developed to determine the risk factors which lead to population decline and to investigate management actions for viable populations. Demographic stochasticity was considered by (a) describing reproduction on an individual basis and (b) distinguishing behavioural patterns according to age and sex. Unknown model parameters were determined by comparing field data and simulated patterns in a specific multi-criteria fashion. We conclude that disturbances such as agricultural management and highway construction are most dangerous to the common hamster in autumn. Complex land management is required which should aim at reducing habitat-specific mortality and favouring the safeguarding of adult and subadult females to protect the most sensitive component of the population. According to the model results, large habitat size is not sufficient for survival, and habitat connectivity may be even more important. Late timing of the harvest and following cultivations was most favourable for population survival.

European hamsters (Cricetus cricetus) show a transient phase of insensitivity to long photoperiods after gonadal regression.

Annual rhythms of body weight and reproduction in the European hamster (Cricetus cricetus) are the result of an interaction between seasonal changes in day length (photoperiod) and seasonal changes in the responsiveness of animals to these photoperiods. The present study demonstrates that under natural conditions European hamsters are not able to perceive long photoperiods (i.e., a 16L:8D cycle) before mid-November. This is an important difference to other hamster species, in which regrowth of the gonads can be stimulated by exposure to long photoperiods at any stage of gonadal regression. The experiments also demonstrate the existence of an annual phase of sensitivity to long photoperiods that starts around mid-November and extends until March/April. During this phase of sensitivity, exposure to a long photoperiod (16L:8D) induced gonadal regrowth within 3 wk. Additional experiments with an accelerated photoperiodic lighting regimen indicated that a photoperiod of approximately 13 h is necessary to stimulate gonadal regrowth. Under natural light conditions in Stuttgart (48.46 degrees N), a photoperiod of 13 h is reached by the beginning of April, which fits well with the finding that the majority of animals kept under a natural light:dark cycle had well-developed gonads by the end of April. Nevertheless, these animals showed a rather variable timing of gonadal regrowth, ranging from early January to late April. This is most likely the result of two processes: first, an endogenous mechanism (photorefractoriness) that induces gonadal recrudescence without any photoperiodic information while the animals are still in their hibernation burrows, and second, a direct stimulatory effect of long photoperiods.

Multiple bottlenecks in threatened western European populations of the common hamster Cricetus cricetus (L.)

Common hamsters Cricetus cricetus (L.)show a highly fragmented distributionpattern across Europe. Over the last decades,human influence caused significant populationdeclines in particular at the western rangeboundary. Despite the initiation of breedingand release programs the genetic structure anddiversity of European common hamsterpopulations is largely unknown. In this study,hamsters from ten localities in five Europeancountries were investigated. Mitochondrialcontrol region was sequenced from 145 animalsrepresenting all sampled populations. 385hamster were screened for polymorphisms at 11microsatellite loci. Both marker systemsrevealed extensive genetic differentiationamong European common hamsters. Westernpopulations displayed very low levels of mtDNAdiversity (H = 0 − 0.2, Alsace, Limburg,Flanders, Baden-Wuerttemberg) compared toeastern populations from Saxony-Anhalt,Thuringia and Southern Moravia (H = 0.663− 0.816). Microsatellite analyses revealed asimilar pattern with low to moderate diversityvalues in western hamsters (A = 1.636 −5.364; H e = 0.111 − 0.504) and highlevels of polymorphism in eastern hamsters(A = 8.909 − 9.818; H e = 0.712− 0.786). High microsatellite based F STmeasures (up to 0.635) suggest a typical islandmodel of distribution with no current gene flowbetween most areas. Western hamster populationsexhibit obvious similarities in mitochondrialhaplotype and microsatellite alleledistributions. Gene trees group westernhamsters consistently together on the samebranch but bootstrap values never reachedsignificance. There are strong indications thatlow diversity in western populations ispartially caused by a joint historic founderevent and not only by recent population breakdowns. Overlapping mitochondrial haplotypesprove a close association between westernhamsters and animals from the east German rangein the recent past which does not support theexistence of a separate subspecies C. c.canescens in Europe. Hamsters from southernMoravia emerged as the genetically mostdistinguished population and could be part of a different genetic lineage in Europe.