Shrews (Sorex spp.) somatometry and reproduction in Slovakia

The morphometrics and reproduction of shrews (Sorex araneus, S. minutus, S. alpinus) was studied in Slovakia. Significant differences in weight, body length and tail length were recorded in adult and subadult shrews. Adult individuals and males had higher mean somatometric values (apart from tail length of subadults). The hind foot length was the least variable characteristic, which can be considered as the most stable taxonomic somatic characteristic of shrews. Weight and body length varied considerably. Values of somatic characteristics in S. araneus and S. minutus increased with increasing altitude, apart from hind foot length in S. araneus, which decreased with increasing altitude. The values of somatic characteristics declined with increasing continentality, but tail length gradually increased in the direction west — east at the highland level. Sorex minutus was characterized by the greatest reproductive activity (length of reproductive cycle April–October, average number of embryos 6.97). The lowest reproductive activity was observed in S. alpinus (average number of embryos 5.72). The mating season of S. araneus began at the end of March and ended in August with an average number of embryos of 6.12.     

Genomic versus chromosomal polytypy in studies of mitochondrial and nuclear DNA markers in the <Emphasis Type="Italic">Microtus arvalis</Emphasis> group

Common voles of the Microtus arvalis group distributed over the territory of European Russia are represented by three karyotypic categories, i.e., sympatric sibling species with 2n = 46 and 54, and two allopatric karyoforms in one of them, 2n = 46. For each category, molecular markers were found. For two 46-chromosome forms (arvalis and obscurus), iDNA was for the first time studied in karyotyped and non-karyotyped specimens for a parapatric hybrid zone, where high diversity of intermediate karyotypes was recorded. Preferential migration of the mitochondrial markers in arvalis and significant differences in the cline width for chromosomal and nuclear markers in obscurus were shown. The hybrid zone examined exhibited unusual combination of such features as the practically complete absence of “pure” representatives of the original parental forms and a clear deficiency of the first generation hybrids. The mtDNA divergence for the arvalis and obscurus karyoforms (4.6%) is comparable to the lowest limit for interspecies differences within the large and complex genus Microtus.     

Spatio‐temporal covariation in abundance between the cyclic common vole Microtus arvalis and other small mammal prey species

Populations of the common vole Microtus arvalis in mid‐western France show cyclic dynamics with a three‐year period. Studies of cyclic vole populations in Fennoscandia have often found inter‐specific synchrony between the voles and other small mammals which share the voles' predators. Although predators are central to the favoured mechanism to explain Fennoscandian vole cycles and the spatial variation of small mammal populations, their role in vole cycles elsewhere, including France, is less clear. Establishing whether alternative prey species in France cycle in parallel with voles as they do in Fennoscandia is thus an important step towards understanding the generality of predators' influence on cyclic vole populations. We applied spatial and temporal autocorrelation and cross‐correlation methods to French populations of M. arvalis and two sympatric non‐cyclic small mammal species, Apodemus sylvaticus and Crocidura russula. Patterns of time‐lagged cross‐correlation between the abundance of M. arvalis and the other two species suggested synchrony in their dynamics beyond that expected of stochastic environmental variation, and indicated a weak three‐year cycle in A. sylvaticus and C. russula that was in phase with that of M. arvalis. We interpret the synchrony between these species as the effect of shared predators and environmental stochasticity. Abundance within species showed weak spatial autocorrelation in June at scales consistent with dispersal being the mechanism responsible, but a more general lack of spatial structure within and between species was consistent with the strong spatial synchrony at regional scales often found in fluctuations of small mammal abundance.     

Dental Variation in Sibling Species <Emphasis Type="Italic">Microtus arvalis</Emphasis> and <Emphasis Type="Italic">M. rossiaemeridionalis</Emphasis> (Arvicolinae,Rodentia): Between-Species Comparisons and Geography of Morphotype Dental Patterns

The data on dental variability in natural populations of sibling species of common voles (“arvalis” group, genus Microtus) from European and Asian parts of the species’ ranges are summarized using a morphotype-based approach to analysis of dentition. Frequency distributions of the first lower (m1) and the third upper (M3) molar morphotypes are analyzed in about 65 samples of M. rossiaemeridionalis and M. arvalis represented by arvalis and obscurus karyotypic forms. Because of extreme similarity of morphotype dental patterns in the taxa studied, it is impossible to use molar morphotype frequencies for species identification. However, a morphotype-based approach to analysis of dental variability does allow analysis of inter-species comparisons from an evolutionary standpoint. Three patterns of dental complexity are established in the taxa studied: simple, basic (the most typical within the ranges of both species), and complex. In M. rossiaemeridionalis and in M. arvalis obscurus only the basic pattern of dentition occurs. In M. arvalis arvalis, both simple and basic dental patterns are found. Analysis of association of morphotype dental patterns with geographical and environmental variables reveals an increase in the number of complex molars with longitude and latitude: in M. arvalis the pattern of molar complication is more strongly related to longitude, and in M. rossiaemeridionalis—to latitude. Significant decrease in incidence of simple molars with climate continentality and increasing aridity is found in M. arvalis. The simple pattern of dentition is found in M. arvalis arvalis in Spain, along the Atlantic coast of France and on islands thereabout, in northeastern Germany and Kirov region in European Russia. Hypotheses to explain the distribution of populations with different dental patterns within the range of M. arvalis sensu stricto are discussed.     

Familiarity and partner preferences in female common voles, <Emphasis Type="Italic">Microtus arvalis</Emphasis>

Captive female common voles (Microtus arvalis) had a clear social preference for familiar males in a standard preference test. Cohabitation for a short period resulted in preferences for familiar partners, and females spent eight times more time in body contact with a familiar male than with an unfamiliar male. Females also displayed stranger-directed aggression. Our results suggest that the common vole is a species with selective partner preferences and a tendency to form tight social relationships and stable male–female associations.     

Morphometric differentiation of the moor frog (Rana arvalis Nilss.) in Central Europe

Morphometric variation of 11 characters was studied in 14 samples of Rana arvalis from allopatric population groups in Central Europe, representing two subspecies formerly recognised: R. a. arvalis and R. a. wolterstorffi. All samples from Poland (nine) were collected from the area, which is believed to be populated by the nominal form. In addition, the isolated population of R. arvalis from the Eastern Carpathians of Romania was classified to that form. All the Hungarian samples fall into the range of R. a. wolterstorffi. No significant differences in body size between sexes and among the populations from the three geographic regions (Poland, Hungary and Romanian Eastern Carpathians) were found. Multivariate analysis of the differences in body shape among groups showed that the populations from Hungary differed from the nominal form mainly in the relative hindlimb length. However, substantial overlap in overall shape differences resulted in a relatively low percentage of correct classifications to the respective geographic groups in the Discriminant Analysis. Large intrapopulation variation in the values of the two ratios (SVL/TL and TL/IMT) formerly used for differentiate the two European subspecies of R. arvalis makes them unreliable characters for distinguishing the two forms. The pattern of morphometric variation does not match the overall genetic divergence of the R. arvalis populations, which suggests that the body shape differences in this species result from the phenotypic plasticity correlated with local climatic factors.     

Microsatellite markers for the common vole (<Emphasis Type="Italic">Microtus arvalis</Emphasis>) and their cross-species utility

Fragmentation of natural habitats of the common vole (Microtus arvalis) provides an excellent model system to study the consequences of restricted gene flow and small population sizes for isolated populations. Here we describe the isolation and characteristics of 10 autosomal and one X-linked microsatellite marker. These new markers were tested in 24 voles from a natural population in eastern Germany. Loci were highly polymorphic with numbers of alleles per locus ranging from three to 26 and expected heterozygosities from 0.51 to 0.97. All loci except for the X-linked locus Mar105 followed Hardy–Weinberg expectations. Cross-species amplifications revealed that most loci were polymorphic as well in M. agrestis, M. thomasi, and M. pennsylvanicus.     

Isolation and characterization of polymorphic microsatellite loci in the field vole,Microtus agrestis,and their cross‐utility in the common vole,Microtus arvalis

We developed nine polymorphic microsatellite loci for the field vole, Microtus agrestis. The number of alleles ranged from five to 15 and observed heterozygosities ranged from 0.40 to 1.00. We also tested the microsatellite loci for amplification and polymorphism in the congeneric species Microtus arvalis. Five of the nine loci were successfully analysed in this species. The microsatellite markers will be employed in studies of reproductive success and fine‐scale spatial genetic structure.     

Effects of avpr1a length polymorphism on male social behavior and reproduction in semi‐natural populations of prairie voles (Microtus ochrogaster)

Intraspecific variation in sociosexual behavior has typically been investigated in the context of its relationship with environmental factors, but neurogenetic factors can also influence sociosexual behavior. In laboratory studies of prairie voles (Microtus ochrogaster), length polymorphism of microsatellite DNA within the gene (avpr1a) encoding the vasopressin 1a receptor is correlated with variation in male sociosexual behavior. However, field studies of prairie voles have found the relationship between male avpr1a microsatellite allele length and sociosexual behavior to be more ambiguous, possibly because most males had alleles of intermediate length. We tested the hypothesis that avpr1a microsatellite allele length mediates male sociosexual behavior in field settings by releasing voles into field enclosures where every male possessed two avpr1a microsatellite alleles at least one standard error longer or shorter than the mean length in their population of origin. Voles from an Illinois and Kansas population were examined separately as social monogamy appears more prevalent in the Illinois population. Illinois males with long avpr1a microsatellite alleles had smaller home ranges and overlapped a greater proportion of the home range of the female that they overlapped the most. Kansas males showed the opposite pattern. Illinois, but not Kansas, males with long avpr1a microsatellite alleles sired offspring with more females and sired more litters. Our results support the hypothesis that genetic variation associated with the avpr1a gene plays a role in mediating male prairie vole sociosexual behavior in nature. However, the relationship between specific male behaviors and male avpr1a microsatellite allele length sometimes differed significantly between Kansas and Illinois voles, suggesting relationships between specific male sociosexual behaviors and polymorphism associated with the avpr1a locus are complex, possibly involving specific nucleotide sequences or other population‐specific genetic differences.     

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.     

A complex scenario of glacial survival in Mediterranean and continental refugia of a temperate continental vole species (Microtus arvalis) in Europe

The role of glacial refugia in shaping contemporary species distribution is a long-standing question in phylogeography and evolutionary ecology. Recent studies are questioning previous paradigms on glacial refugia and postglacial recolonization pathways in Europe, and more flexible phylogeographic scenarios have been proposed. We used the widespread common vole Microtus arvalis as a model to investigate the origin, locations of glacial refugia, and dispersal pathways, in the group of “Continental” species in Europe. We used a Bayesian spatiotemporal diffusion analysis (relaxed random walk model) of cytochrome b sequences across the species range, including newly collected individuals from 10 Iberian localities and published sequences from 68 localities across 22 European countries. Our data suggest that the species originated in Central Europe, and we revealed the location of multiple refugia (in both southern peninsulas and continental regions) for this continental model species. Our results confirm the monophyly of Iberian voles and the pre-LGM divergence between Iberian and European voles. We found evidence of restricted postglacial dispersal from refugia in Mediterranean peninsulas. We inferred a complex evolutionary and demographic history of M. arvalis in Europe over the last 50,000 years that does not adequately fit previous glacial refugial scenarios. The phylogeography of M. arvalis provides a paradigm of ice-age survival of a temperate continental species in western and eastern Mediterranean peninsulas (sources of endemism) and multiple continental regions (sources of postglacial spread). Our findings also provide support for a major role of large European river systems in shaping geographic boundaries of M. arvalis in Europe.     

Patterns of investment in reproductive and somatic tissues in the loliginid squid <Emphasis Type="Italic">Loligo forbesii</Emphasis> and <Emphasis Type="Italic">Loligo vulgaris</Emphasis> in Iberian and Azorean waters

The veined squid, Loligo forbesii, is found throughout the northeast Atlantic, including the waters off the Iberian Peninsula, and is a socio-economically important cephalopod species, sustaining several small-scale commercial and local artisanal fisheries. This study uses Iberian and Azorean trawl survey and fishery landings data from 1990 to 1992 and employs additive modelling to examine the relationships amongst somatic growth, season and gonad growth, in an attempt to determine the relative importance of intrinsic (e.g. nutritional state and body size) and extrinsic (temperature and daylight) factors which contribute to maturation in L. forbesii. We compare the results with those from a comparative analysis of contemporaneous data on Loligo vulgaris from the Iberian coast, and with a re-analysis of previously published results for L. forbesii in Scottish waters. Reproductive organ weight in both sexes of L. forbesii from all ports shows seasonal patterns with a fall/winter peak in maturation, as is expected with the animals’ year-long life cycle. Two maturity peaks (spring and winter) were found for both Azores L. forbesii males and females, possibly evidence of two breeding cohorts, with males maturing approximately 1 month earlier than females in both seasons. For L. vulgaris, three annual peaks in reproductive weight were identified. With the exception of L. forbesii males from Scottish waters, in all study animals, the partial effect of mantle length and mantle weight on reproductive weight is positive up to large body sizes. The relationship between nutritional status and reproductive weight is also generally positive. Geographic variation in the relationships, as seen between Scottish males and samples from the other study areas, is hypothesised to be largely attributable to local differences in environmental conditions (productivity, food availability, temperature, upwelling), although differences between L. forbesii from the Azores, Scotland and mainland Europe may also relate to previously documented genetic differences.     

Patterns of variation in Microtus arvalis and Microtus agrestis populations from Middle to Late Pleistocene in southwestern Europe

Fifteen paired fossil populations of Microtus arvalis and Microtus agrestis from southwestern Europe have been analysed from a morphological and morphometric point of view. The sites under consideration are located in the northern Iberian Peninsula and southern France, from the Middle Pleistocene to the end of the Late Pleistocene. The aim of this study is to stress once again the importance of keeping these two species separated in the fossil record in order to recognize specific trends of evolution and divergence and to obtain more precise information on palaeoclimatic and palaeoenvironmental conditions. It was possible to observe remarkable intraspecific differences between Middle and Late Pleistocene populations of both species. Furthermore, in synchronic co-specific populations from the Late Pleistocene, climatic and geographic conditions seem to exert a major influence in shaping intraspecific changes in dental pattern.     

Sex‐specific reproductive investment of summer spawners of Illex argentinus in the southwest Atlantic

Energy investment in reproduction and somatic growth was investigated for summer spawners of the Argentinean shortfin squid Illex argentinus in the southwest Atlantic Ocean. Sampled squids were examined for morphometry and intensity of feeding behavior associated with reproductive maturation. Residuals generated from length‐weight relationships were analyzed to determine patterns of energy allocation between somatic and reproductive growth. Both females and males showed similar rates of increase for eviscerated body mass and digestive gland mass relative to mantle length, but the rate of increase for total reproductive organ weight relative to mantle length in females was three times that of males. For females, condition of somatic tissues deteriorated until the mature stage, but somatic condition improved after the onset of maturity. In males, there was no correlation between somatic condition and phases of reproductive maturity. Reproductive investment decreased as sexual maturation progressed for both females and males, with the lowest investment occurring at the functionally mature stage. Residual analysis indicated that female reproductive development was at the expense of body muscle growth during the immature and maturing stages, but energy invested in reproduction after onset of maturity was probably met by food intake. However, in males both reproductive maturation and somatic growth proceeded concurrently so that energy allocated to reproduction was related to food intake throughout the process of maturation. For both males and females, there was little evidence of trade‐offs between the digestive gland and reproductive growth, as no significant correlation was found between dorsal mantle length‐digestive gland weight residuals. The role of the digestive gland as an energy reserve for gonadal growth should be reconsidered. Additionally, feeding intensity by both males and females decreased after the onset of sexual maturity, but feeding never stopped completely, even during spawning.     

Sex determination of Microtus mandarinus mandarinus is independent of Sry gene

PCR was performed with primers corresponding to the Sry HMG-box of the mouse and eight Microtus species. Primers for the SALL4 gene and the ZFY/ZFX gene were used as positive controls. None of these sets of primers can amplify any homologous segment of the Sry gene in the genomic DNA of Microtus mandarinus mandarinus, but both can amplify the Sry HMG-box in the male mouse, SALL4 bands, and ZFY/ZFX bands in both male and female M. m. mandarinus and mouse. Southern blotting was also used. We used primers for the mouse Sry HMG-box to amplify the Sry HMG-box of the mouse, Microtus arvalis (Microtus), and Pitymys duodecimcostatus (Microtus). The probes were labeled with digoxigenin using PCR after being sequenced. Southern blots were used to detect the genomic DNA of M. m. mandarinus using alkaline phosphatase detection. The results showed that there was a 3.95-kb-blotting band in positive controls: mouse, Microtus arvalis, and Pitymys duodecimcostatus. However, no homologous sequence of the Sry HMG-box was detected in the genomic DNA of M. m. mandarinus. Therefore, we speculate that the Sry HMG-box of M. m. mandarinus is absent or had a big change; sex determination of M. m. mandarinus is independent of Sry. The sex determination mechanism without Sry of M. m. mandarinus is also discussed.     

青藏高原东南缘陇蜀杜鹃当年生小枝茎叶性状对海拔变化的响应

通过在青藏高原东南缘的岷江源区三处高山林草交错带采集陇蜀杜鹃当年生小枝,测量小枝的茎长、茎粗与茎生物量,沿海拔梯度自然分布的空间变化对比其当年生小枝的茎结构与生物量及其相互关系,接着比较了总叶质量和比叶面积的变化,最后通过典范对应分析(CCA)探究小枝茎叶性状与土壤因子的相关关系,有助于理解陇蜀杜鹃适应异质环境的生态适应对策。结果表明:(1)除弓杠岭外,斗鸡台与卡卡山土壤因子在海拔间差异显著,相似海拔不同山地间土壤因子也存在显著差异。(2)除卡卡山高海拔比叶面积显著小于低海拔外,其他样地的小枝茎性状(茎长、茎粗、比茎长和茎生物量)和叶性状(总叶质量和比叶面积)在海拔间并无显著差异,相似海拔不同坡体间茎粗、茎生物量以及比茎长差异也未达到显著水平(P>0.05),但弓杠岭(3963 m)的茎长显著大于卡卡山(3921 m)(P<0.05)。(3)小枝茎长、茎粗与茎生物量之间均为异速生长关系,且茎生物量累积速率大于茎长和茎粗增加的速率,且茎长的增加速率约为茎粗的2.8倍。(4)CCA排序结果表明,11个土壤环境因子中,碳含量、碳氮比、有机碳含量、总磷和容重对植物性状有显著的影响,但在海拔及不同山体间影响小枝茎叶性状的土壤因子不同。由此可知,较小的海拔梯度变化对小枝茎叶性状影响较小,土壤因子是导致小枝茎叶性状差异的重要原因之一。     

The Influence of Sire Presence on Survival and the Growth Rate of Juvenile Common Voles <Emphasis Type="Italic">Microtus arvalis</Emphasis>

Pup survival and growth rates were monitored to determine whether paternal care potentially contributes to reproductive success of male common voles Microtus arvalis Pallas, 1779. The subjects were 258 pups from 47 litters obtained from adult voles trapped in the wild. Reproducing pairs were formed and divided onto two groups in accordance with the age and parental experience of the reproducing individuals: group I included pairs with subadult males and nulliparous females; group II included pairs with adult males and multiparous females. Each of the groups was divided into two subgroups: in subgroups Iа (n = 13) and IIа (n= 11), litters were raised by females without sires; in subgroups Ib (n = 12) and IIb (n = 11), litters were raised by both parents. The litter size was recorded at parturition and again when the young were 12, 21, and 30 days old. Pups in each litter were weighed at parturition and also again when the young were 12, 21, and 30 days old. This study has shown that the presence of the sire may negatively affect both survival and growth rates of the pups, but this effect is dependent on the age of the reproducing individuals.     

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.     

Meiosis in gray voles of the subgenus <Emphasis Type="Italic">Microtus</Emphasis> (Rodentia,Arvicolinae) and in their hybrids

The results of light and electron microscopic (EM) studies of meiosis in Microtus arvalis males of the karyoform “arvalis” (2n = 46, NFa = 80), in hybrids between the chromosomal forms arvalis and obscurus (2n = 46, NFa = 68), in M. rossiaemeridionalis voles (2n = 54, NFa = 54), and in a hybrid between the species M. rossiaemeridionalis and kermanensis (2n = 54, NFa = 54) are presented. SC (synaptonemal complex) karyotypes of the parental forms and the hybrids were constructed on the basis of measurements of the length of autosomal SCs revealed by the EM analysis in spermatocytes at the stage of middle pachytene. The SC karyotypes of M. arvalis and the hybrids ♀ obscurus × ♂ arvalis consist of 22 synaptonemal complexes of autosomal bivalents and the axial elements of the synaptonemal complexes of the sex chromosomes X and Y. The SC karyotypes of M. rossiaemeridionalis and the hybrid M. rossiaemeridionalis × M. kermanensis consist of 26 synaptonemal complexes of autosomal bivalents and a sex bivalent; they differ only in the length of the Y chromosome axis (Y chromosome in the hybrid was inherited from M. kermanensis). Asynaptic configurations of the autosomal SCs were not observed in the hybrids. The SC axial elements of the X and Y chromosomes in the parental forms and in the hybrids were located close to each other throughout pachytene, but they did not form a synaptic region. The normal synapsis in sterile hybrids (M. rossiaemeridionalis × M. kermanensis) and the behavior of the sex chromosomes in meiosis in fertile and sterile hybrids are discussed in the context of specific features of meiosis and reproductive isolation.     

Isolation of ES-Like Lines of Common Voles of the Genus Microtus from Blastocysts and Germ Cells and as a Result of Fusion of Somatic Cells with Mouse Embryonic Stem Cells

Three and four independent cell lines with limited pluripotency were obtained from the inner cell mass cells of blastocysts and primordial germ cells of common voles, respectively. The results of cytogenetic analysis suggest that all these lines originated from the embryos of F₁ Microtus rossiaemeridionalis × M. arvalis males and had a great number of near-triploid cells already during the early passages. The cells of these lines, like those of the inner cell mass, were characterized by the alkaline phosphatase activity. Nine independent cell lines were obtained as a result of hybridization of the mouse embryonic stem cells and vole splenocytes: eight lines and one line from hybridization with the M. kirgisorum and M. rossiaemeridionalis splenocytes, respectively. The cells of these lines expressed some properties of embryonic stem lines had a chromosome complement similar to the sum of two initial diploid sets of the mouse and vole.