Dampening of population cycles in voles affects small mammal community structure,decreases diversity,and increases prevalence of a zoonotic disease

Long‐term decline and depression of density in cyclic small rodents is a recent widespread phenomenon. These observed changes at the population level might have cascading effects at the ecosystem level. Here, we assessed relationships between changing boreal landscapes and biodiversity changes of small mammal communities. We also inferred potential effects of observed community changes for increased transmission risk of Puumala virus (PUUV) spread, causing the zoonotic disease nephropatica epidemica in humans. Analyses were based on long‐term (1971–2013) monitoring data of shrews and voles representing 58 time series in northern Sweden. We calculated richness, diversity, and evenness at alpha, beta, and gamma level, partitioned beta diversity into turnover (species replacement) and nestedness (species addition/removal), used similarity percentages (SIMPER) analysis to assess community structure, and calculated the cumulated number of PUUV‐infected bank voles and average PUUV prevalence (percentage of infected bank voles) per vole cycle. Alpha, beta, and gamma richness and diversity of voles, but not shrews, showed long‐term trends that varied spatially. The observed patterns were associated with an increase in community contribution of bank vole (Myodes glareolus), a decrease of gray‐sided vole (M. rufocanus) and field vole (Microtus agrestis) and a hump‐shaped variation in contribution of common shrew (Sorex araneus). Long‐term biodiversity changes were largely related to changes in forest landscape structure. Number of PUUV‐infected bank voles in spring was negatively related to beta and gamma diversity, and positively related to turnover of shrews (replaced by voles) and to community contribution of bank voles. The latter was also positively related to average PUUV prevalence in spring. We showed that long‐term changes in the boreal landscape contributed to explain the decrease in biodiversity and the change in structure of small mammal communities. In addition, our results suggest decrease in small mammal diversity to have knock‐on effects on dynamics of infectious diseases among small mammals with potential implications for disease transmission to humans.     

Protein polymorphisms and their genetic control in the red-backed vole, Clethrionomys rufocanus bedfordiae

Twenty enzymatic and non-enzymatic proteins in a wild population of red-backed voles, Cletrionomys rufocanus bedfordiae , were investigated by electrophoresis. Seven enzymatic and non-enzymatic protein systems were found to be polymorphic. Breeding data indicated that the mode of inheritance of the enzyme systems ME-1, ME-2, GPD and EST were consistent with a Mendelian law. Two systems, 6 PGD and SOD, were estimated to be genetically controlled from the electrophoretic patterns and mother-offspring comparison of phenotypes. In the Tf system two new additional phenotypes were observed, but their inheritance could not be elucidated. Gene frequencies at seven loci were also investigated in 88 animals. There was no significant deviation from Hardy-Weinberg equilibrium.     

浅谈田鼠亚科动物的种群调节─—食物、营养及复合因子假说

浅谈田鼠亚科动物的种群调节─—食物、营养及复合因子假说姜永进,王德华（中国科学院西北高原生物所,西宁８１０００１）（北京师范大学生物系,１００８７５）ＲｅｇｕｌａｔｉｏｎｏｆＶｏｌｅＰｏｐｕｌａｔｉｏｎ：ＩｎｖａｌｉｄｉｔｙｏｆｔｈｅＦｏｏｄ,Ｎｕｔ...     

田鼠亚科啮齿动物的社会组织、交配制度和栖息地的关系

田鼠亚科的两种啮齿动物黄腹田鼠(prairie vole,Microtus ochrogaster)和草甸田鼠(meadow vole,M.pennsylvanicus)是社会组织完全不同的两个种。黄腹田鼠原始栖息地在北美北部中央大片毗连的草原上,生境较稳定。该种易于接触,其交配为一夫一妻制,并成对结合。雌雄鼠共居在同一巢穴里,雌鼠只与配对雄鼠交配,雄鼠回避非配对的外来雌鼠,并分担巢穴的营造和维修,同时也照管幼仔,包括饲养、聚集和挽救。幼体断乳后,多数仍留在巢穴里,并协助照管下一窝幼仔,不参加繁殖,只有那些从家族群中扩散出去,并与无亲缘关系的雄鼠交配的雌性青年鼠才能繁殖后代。这种交配制度的作用是扩散种群,子代为寻求婚配而从家族群中离去,从而避免局部种群密度增高,以及由此造成的食物短缺。由于繁殖对是由非亲缘关系的个体结合而成,避免了近亲繁殖及由此带来的遗传性有害影响。     

Social environment regulates corticotropin releasing factor, corticosterone and vasopressin in juvenile prairie voles

Stressful social conditions, such as isolation, that occur during sensitive developmental periods may alter present and future social behavior. Changes in the neuroendocrine mechanisms closely associated with affiliative behaviors and stress reactivity are likely to underlie these changes in behavior. In the present study, we assessed the effects of post-weaning social housing conditions on the neuropeptides arginine vasopressin (AVP) and oxytocin (OT), and components of the hypothalamic-pituitary-adrenal axis (corticotropin releasing factor: [CRF], and corticosterone: [CORT]) in the prairie vole (Microtus ochrogaster), a socially monogamous bi-parental rodent. Following weaning at 21 days of age, prairie voles were maintained in one of three housing conditions: social isolation (isolate), paired with a same sex sibling (sibling) or paired with a stranger (stranger) of the same sex and age. Housing conditions were maintained for either 4 or 21 days. Central CRF, AVP and OT immunoreactivity (ir) were quantified and circulating plasma CORT, AVP and OT were assayed. Isolated voles had higher CRF-ir in the paraventricular nucleus of the hypothalamus (PVN) compared with sibling and stranger housed voles. Plasma CORT was significantly higher in isolates. AVP-ir was significantly lower in the PVN of isolate females compared to either sibling females or stranger females. However, AVP-ir was significantly higher in the supraoptic nucleus (SON) of isolates compared to siblings. There were no differences in central OT-ir or plasma OT. These results identify neuroendocrine mechanisms which respond to isolation and potentially modulate behavior.     

Cadmium,zinc and iron interactions in the tissues of bank vole <Emphasis Type="BoldItalic">Clethrionomys glareolus</Emphasis> after exposure to low and high doses of cadmium chloride

In present study, bank voles Clethrionomys glareolus were peritioneally injected with different doses of cadmium, 0, 1.5, 3.0 mg Cd/kg body mass. Animals were sacrificed on the 21st day after cadmium exposure and the liver and kidney were obtained for cadmium, zinc and iron analysis using atomic absorption spectrometry. Results showed that cadmium had accumulated in the tissues according to dosage and sex. Cadmium affected the survival and body masses of dosed females. Cadmium decreased the iron concentrations in the liver of voles, whereas zinc concentrations increased in both the kidney and liver.     

Detection of aromatase, androgen, and estrogen receptors in bank vole spermatozoa

Spermatozoa are highly specialized cells which transport a single-copy haploid genome to the site of fertilization. Before this, spermatozoa undergo a series of biochemical and functional modifications. In recent years, the crucial role of androgens and estrogens in proper germ cell differentiation during spermatogenesis has been demonstrated. However, their implication in the biology of mature male gametes is still to be defined. Our study provides evidence for the first time that aromatase, the androgen receptor (AR), as well as the estrogen receptors α and β (ERα and ERβ), are present in bank vole spermatozoa. We demonstrated the region-specific localization of these proteins in bank vole spermatozoa using confocal microscopy. Immunoreactive aromatase was observed in the proximal head region and in both the proximal and distal tail regions, whereas steroid hormone receptors were found only in the proximal region of the sperm head. Protein expression in sperm lysates was detected by Western blot analysis. Immunohistochemical results were analyzed quantitatively. Our results show that bank vole spermatozoa are both a source of estrogens and a target for steroid hormone action. Moreover, the presence of aromatase and steroid hormone receptors in the bank vole spermatozoa indicates a potential function of these proteins during capacitation and/or the acrosome reaction.     

Polyandry enhances offspring survival in an infanticidal species

The adaptive significance of polyandry is an intensely debated subject in sexual selection. For species with male infanticidal behaviour, it has been hypothesized that polyandry evolved as female counterstrategy to offspring loss: by mating with multiple males, females may conceal paternity and so prevent males from killing putative offspring. Here we present, to our knowledge, the first empirical test of this hypothesis in a combined laboratory and field study, and show that multiple mating seems to reduce the risk of infanticide in female bank voles Myodes glareolus. Our findings thus indicate that females of species with non-resource based mating systems, in which males provide nothing but sperm, but commit infanticide, can gain non-genetic fitness benefits from polyandry.     

根田鼠母体摄食经历对幼体食物选择的影响

社会学习是动物的一种可塑性行为表型,能使动物个体获得提高其适合度的行为模式。母体对幼体的食性形成具有重要的影响。本文以栖息于青藏高原的根田鼠作为研究对象,在实验室条件下,根田鼠母体怀孕后期及哺乳期分别供给以0.01%糖精或0.1%橘子汁处理的食物,当幼体断乳时,同时供给断乳幼体糖精和橘子汁分别处理的食物,测定其食物选择。结果表明:根田鼠母体在怀孕期和哺乳期摄食经橘子汁处理的食物,断乳幼体在同时供给经橘子汁处理的食物和糖精处理的食物时,断乳幼体喜食经橘子汁处理的食物;而母体在怀孕期和哺乳期摄食经糖精处理的食物,断乳幼体在同时供给根田鼠断乳幼体经橘子汁处理和糖精处理的食物时,断乳幼体喜食经糖精处理的食物。说明根田鼠在断乳后仍喜食母体在怀孕期和哺乳期摄食过的食物种类。根田鼠栖息于季节性变化剧烈的环境中,幼体通过母体尽早学习食物选择是一种可塑性表型方式,利于其获得适应栖息地的行为模式。     

Small mammal responses to biosolids on grazed rangelands in British Columbia

Grasslands are globally declining due to habitat conversion, overgrazing, climate change, and changes in fire and drought regimes. Degraded grasslands are less able to support wildlife species, which contributes to the imperilment of many species. Biosolids are used by some ranchers as an organic amendment to support more plant growth and in turn more livestock. We worked on a large cattle ranch in central British Columbia, Canada, to determine how biosolids amendment affected small mammal populations, as mice and voles are major prey for many predators and contribute to seed dispersal and underground dynamics. We found that biosolids-amended pastures had more grass cover and supported fewer deermice (Peromyscus maniculatus) than did unamended pastures. Voles were scarce, likely due to a cyclic low. Although we sampled sites that had had biosolids applied 1 or 3 years prior to our work started, deermouse populations were similarly low across these sites. The reduction in deermice on sites with biosolids relative to unamended sites could be a signal of habitat restoration, because deermice prefer disturbed habitats rather than ones with high plant cover. Grass cover was more than twice as high on sites amended with biosolids, making these sites less suitable for deermice.     

Food provisioning alters infection dynamics in populations of a wild rodent

While pathogens are often assumed to limit the growth of wildlife populations, experimental evidence for their effects is rare. A lack of food resources has been suggested to enhance the negative effects of pathogen infection on host populations, but this theory has received little investigation. We conducted a replicated two-factor enclosure experiment, with introduction of the bacterium Bordetella bronchiseptica and food supplementation, to evaluate the individual and interactive effects of pathogen infection and food availability on vole populations during a boreal winter. We show that prior to bacteria introduction, vole populations were limited by food availability. Bordetella bronchiseptica introduction then reduced population growth and abundance, but contrary to predictions, primarily in food supplemented populations. Infection prevalence and pathological changes in vole lungs were most common in food supplemented populations, and are likely to have resulted from increased congregation and bacteria transmission around feeding stations. Bordetella bronchiseptica-infected lungs often showed protozoan co-infection (consistent with Hepatozoon erhardovae), together with more severe inflammatory changes. Using a multidisciplinary approach, this study demonstrates a complex picture of interactions and underlying mechanisms, leading to population-level effects. Our results highlight the potential for food provisioning to markedly influence disease processes in wildlife mammal populations.     

The influence of climate on morphometric traits of fossil populations of Microtus arvalis and M. agrestis from the Carpathian Basin,northern Hungary

In this study, we analysed morphometrically fossil populations of Microtus arvalis and M. agrestis from eight late Middle to Late Pleistocene archaeological and palaeontological sites in the Carpathian Basin, northern Hungary. The intra‐ and interspecific variations in both species can be related to climatic oscillations linked to the onset of the Eemian interglacial and the first phases of Marine Isotope Stage 5. The size of M. agrestis can be correlated with the presence/absence of relatively humid climatic and environmental conditions and of surface water resources (such as marshes and flooded areas). A possible immigration event of M. arvalis populations into the Carpathian Basin, also related to the Eemian interglacial, is also identified.     

Polymorphic microsatellite loci and PCR multiplexing in the common vole,Microtus arvalis

We isolated and characterized 14 dinucleotide microsatellite loci in the common vole Microtus arvalis (Palas). Two multiplex panels both comprising seven loci were developed. Application to a set of 21 individuals allowed clear and easy characterization of allele sizes except for two loci which were then withdrawn from further analyses. The number of alleles ranged from four to 19 per locus with the observed heterozygosity ranging from 0.55 to 0.95. These sets of microsatellite loci provide high throughput capacity for population genetic studies at a minimum cost.     

褐家鼠肥满度的研究

褐家鼠肥满度的研究杨再学,郭世平（贵州省余庆县植保站,５６４４００）ＲｅｌａｔｉｖｅＦａｔｎｅｓｓｏｆＢｒａｎｄ＇ｓＶｏｌｅ（Ｒａｔｔｕｓｎｏｒｖｅｇｉｃｕｓ）．￥ＹａｎｇＺａｉｘｕｅ;ＧｕｏＳｉｐｉｎｇ（ＹｕｑｉｎｇＣｏｕｎｔｙＰｌａｎｔＰｒｏｔｅ...