Functional response of the least weasel, Mustela nivalis nivalis

We investigated the functional response of the least weasel ( Mustela nivalis nivalis ) in a series of experiments conducted in large outdoor enclosures (0.5 ha). Radiocollared Microtus voles were released in the enclosures at different densities (4, 8, 16 and 100/ha) three days before the release of a radiocollared weasel. During the three-day experiment every vole killed was replaced with another one as soon as possible to retain constant prey density. The results demonstrated type II functional response with the predation rate reaching 50% of the asymptotic rate at a vole density of 15 individuals per ha. More voles were killed at the highest densities than would be expected from the known energy demands of weasels. Female and male voles were killed in proportion to their abundances in the enclosures, and no difference in predation risk was detected between voles released in the enclosure before the weasel (residents) and during the experiment (transients).     

Large-scale spatial and temporal patterns in population dynamics of the stoat, Mustela erminea, and the least weasel, M. nivalis, in Finland

The stoat and the least weasel are specialist predators of small rodents, and therefore their numbers are likely to depend on the availability of voles. These small predators are ecologically alike, but they differ somewhat in their diet. The stoat is larger in size than the least weasel and therefore capable of using a wider variety of prey species, while the least weasel is more restricted to small mammals. Voles in northern Fennoscandia exhibit cyclic dynamics of 3–5 years with large-scale spatial synchrony and geographical trends in cycle length and amplitude. We predicted that the cyclic dynamics of voles are reflected in the dynamics of their predators with slight differences between the stoat and the least weasel. In this study we use snow-tracking data to characterize the dynamics of small mustelids. The data were collected from different parts of Finland using permanent triangle-shaped census routes of 12 km in 1989 to 2003. Population fluctuations of small mustelids were generally multiannually periodic and in synchrony over large areas, but we did not find any clear geographical gradient in the attribute of small mustelid dynamics comparable to those observed in vole population fluctuations. Instead, we found a similar decreasing temporal trend in the abundances of both species as has been recently reported for voles.     

Trade-offs between activity and thermoregulation in a small carnivore,the least weasel Mustela nivalis

We studied factors influencing daily energy expenditures (DEE) of male least weasels (Mustela nivalis) using the doubly labelled water technique. The relationship between ambient temperature and DEE formed a triangular pattern, characterized by invariance of the maximum DEE and an inverse relationship between minimum DEE and temperature. A simple energetic model relating the DEE of male weasels to activity time (AT) and ambient temperature predicted that, across seasons, less than 10 per cent of measurements approach the upper bound of observed DEE. Male weasels were able to maintain a relatively constant maximum energy output across varying temperatures by adjusting their AT to changes in temperature. They achieved maximum energy expenditures in winter due to high thermoregulatory costs, and in spring and summer due to high levels of physical activity. This pattern exemplifies a ‘metabolic niche’ of a small mammal having extremely high energy expenditures primarily driven by ambient temperature.     

Tandemly repeated sequences in the mitochondrial DNA control region and phylogeography of the Pike-Perches Stizostedion

DNA sequences from the mitochondrial DNA control region are used to test the phylogeographic relationships among the pike-perches, Stizostedion (Teleostei: Percidae) and to examine patterns of variation. Sequences reveal two types of variability: single nucleotide polymorphisms and 6 to 14 copies of 10- to 11-base-pair tandemly repeated sequences. Numbers of copies of the tandem repeats are found to evolve too rapidly to detect phylogenetic signal at any taxonomic level, even among populations. Sequence similarities of the tandem repeats among Stizostedion and other percids suggest concerted evolutionary processes. Predicted folding of the tandem repeats and their proximity to termination-associated sequences indicate that secondary structure mediates slipped-strand mispairing among the d-loop, heavy, and light strands. Neighbor-joining and maximum parsimony analyses of sequences indicate that the genus is divided into clades on the continents of North America and Eurasia. Calibrating genetic distances with divergence times supports the hypothesis that Stizostedion dispersed from Eurasia to North America across a North Pacific Beringial land bridge approximately 4 million years before present, near the beginning of the Pliocene Epoch. The North American S. vitreum and S. canadense appear separated by about 2.75 million years, and the Eurasian S. lucioperca and S. volgensis are diverged by about 1.8 million years, suggesting that speciation occurred during the late Pliocene Epoch.     

On co-existence,foraging strategy and the biogeography of weasels and stoats (Mustela nivalis and M. erminea) in Britain

Summary Mustela nivalis and M. erminea, two sympatric species of weasels of superficially similar appearance and habits, have different breeding and foraging strategies associated with the difference in their body size. M. nivalis is more efficient in exploiting small rodent prey, and can breed rapidly to take immediate advantage of rodent peaks, but is vulnerable to local extinction during rodent declines. M. erminea has more generalized food habits, and is the larger and probably the dominant species, but is limited by delayed implantation to producing only one litter a year. M. nivalis is therefore superior in exploitation competition, and erminea in interference competition. We offer the hypothesis that the co-existence of the two species is permitted by a balance of these competitive advantages determined, at a given time or place, by the heterogeneity of the environment and the distribution of the prey fauna. We use this hypothesis to explain cases where co-existence has either broken down or is not recorded (the results of simultaneous introductions to New Zealand and Terschelling Island, and of myxomatosis in Britain, and the distribution of nivalis and Erminea on the offshore islands of Britain). We argue that the diversity and size distribution of the prey fauna of an island (which are both related to its area and isolation) are important in deciding the species and size of mustelids surviving there; for example, we suggest that nivalis was present in Ireland in immediate post-glacial times but became extinct with the lemmings.     

Population genetic structure, phylogeography and spawning philopatry in walleye (Stizostedion vitreum) from mitochondrial DNA control region sequences

Mitochondrial (mt) DNA control region sequences were used to test the genetic and phylogeographic structure of walleye Stizostedion vitreum populations at different geographical scales: among spawning sites, lake basins, lakes, and putative glacial refugia in the Great Lakes region. Sequencing 199 walleye revealed nucleotide substitutions and tandemly repeated sequences that varied in copy number, as well as in sequence composition, in 1200 bp of the mtDNA control region. Variable numbers of copies of an 11-bp tandem repeat showed no geographical patterning and were not used in further analyses. Substitutions in the other areas of the control region yielded 19 haplotypes, revealing phylogeographic structure and significant differences among glacial refugia, lakes, basins and some spawning sites. Differences among spawning populations were consistent with reduced gene flow, philopatry and possible natal homing. Analysis of spawning populations showed consistency of genotypic frequencies among years and between males and females, supporting philopatry in both sexes. The unglaciated plateau in southern Ohio, USA housed a very different haplotype that diverged prior to the Missouri, Mississippi and Atlantic glacial refugia types. Haplotypes from the three refugia colonized the Great Lakes after retreat of the Wisconsin glaciers, and their present distribution reflects the geography of their prior isolation and differential colonization. Populations that became associated with spawning localities appear to have diverged further due to philopatry, resulting in fine-scale phylogeographic structuring.     

东北亚地区野猪种群mtDNA遗传结构及系统地理发生

研究测定了中国东北、华北及四川西部72个野猪(Susscrofa)个体线粒体控制区全序列,并结合GenBank报道的日本野猪(S.s.leucomystax)、琉球野猪(S.s.riukiuanus)72个同源区序列,分析了东北亚地区野猪线粒体DNA的变异及系统地理格局。在东北亚地区野猪的线粒体控制区共发现42个变异位点,均为转换,共定义了34个单元型。单元型之间的系统发生分析表明,东北亚地区野猪来自同一祖先。东北亚地区野猪现生种群具有显著的种群遗传结构,其中日本野猪与分布于中国东北地区的东北野猪之间亲缘关系较近;而琉球野猪则与华北野猪间亲缘关系较近,与日本野猪和东北野猪间的关系相对较远。嵌套进化枝系统地理分析(Nestedcladephylogeographicalanalysis,NCPA)表明:东北亚地区野猪由同一祖先经过长距离的迁徙而形成现生各种群(或亚种);琉球野猪应起源于大陆野猪,其种群演化可能经历了片断化事件;华北野猪呈现南部种群遗传多样性高的特点,其种群内部曾经历了一次分布区由南向北的扩张     

Studies of the metabolism,food consumption and assimilation efficiency of a small carnivore,the weasel (Mustela nivalis L.)

Summary The average respiratory quotient of weasels was 0.73. There were significant differences in average daily metabolic rate (ADMR) between the sexes and six experimental temperatures. As temperature decreased the mean ADMR increased, with a relatively greater rise for females. Regression equations of ADMR on temperature were Y=483.2–9.6X kcal/kg/day for males, and Y=625.3–15.0X kcal/kg/day for females. The minimum metabolic rate measured for males was 6.6 kcal/kg/h, and the maximum 25.7 kcal/kg/h. The relationship between ADMR and body weight varied with different temperatures, but was consistent with the hypothesis that ADMR was proportional to metabolic weight. The energetic costs of activity for my captive weasels were more than 20% of their daily total energy expenditure. Data on metabolism supported the conclusion that long, thin mustelids lose heat faster than normally-shaped mammals of the same weight.The calorific contents of foods, faeces and urine from feeding trials were determined. There were significant differences in the calorific content of faeces between the sexes, and of faeces and urine between diets.Four natural foods (Microtus, Apodemus, rabbit, starling) were offered during feeding trials. Daily food consumption varied between the diets, but small weasels always ate relatively more than large ones. Mean consumption was 0.33 g/g/day for males, and 0.36 g/g/day for females. Weasels on low-bulk diets (rabbit, starling) lost at least as much energy in urine as in faeces. There were significant differences in assimilation efficiency between the sexes and diets. The average efficiency for males was 78.2%, and 79.8% for females. Bulky foods lowered assimilation efficiencies by up to 9%.Daily energy requirements for maintenance calculated from ADMR data were compared with those from feeding trials. On the Microtus diet weasels expended 18.6–30.1% more energy on maintenance than predicted by the ADMR results, whereas on the other diets they expended 2.7–31.4% less energy. Estimates from ADMR data were probably more accurate.     

Phylogeographic study of brown trout from Serbia,based on mitochondrial DNA control region analysis

In order to illuminate the phylogeography of brown trout (Salmo trutta) populations in the Balkan state of Serbia, the 561 bp 5''-end of mtDNA control region of 101 individuals originating from upland tributaries of the Danubian, Aegean and Adriatic drainages were sequenced and compared to corresponding brown trout sequences obtained in previous studies. Among 15 haplotypes found, 14 were considered native, representing the Danubian and Adriatic lineages of the brown trout, while one haplotype (ATcs1), found only in two individuals originating from two stocked rivers, corresponded to the Atlantic lineage and was considered introduced. Native haplotypes exhibited a strong geographic pattern of distribution: the Danubian haplotypes were strictly confined to the Danubian drainage, while the Adriatic haplotypes dominated in the Aegean and Adriatic drainages; most of the total molecular variance (69%) was attributed to differences among the drainages. Phylogenetic reconstruction, supplemented with seven haplotypes newly described in this study, suggested a sister position of the Atlantic-Danubian and Adriatic-Mediterranean-marmoratus ("southern") phylogenetic group, and pointed to the existence of a distinct clade, detected within the "southern" group. The data obtained confirmed our expectation of the existence of high genetic diversity in Balkan trout populations, and we recommend more widespread surveys covering trout stocks from the region.     

Variability of the human mitochondrial DNA control region sequences in the Lithuanian population

The Lithuanians and Latvians are the only two Baltic cultures that survived until today. Since the Neolithic period the native inhabitants of the present-day Lithuanian territory have not been replaced by any other ethnic group. Therefore the genetic characterization of the present-day Lithuanians may shed some light on the early history of the Balts. We have analysed 120 DNA samples from two Lithuanian ethnolinguistic groups (Aukstaiciai and Zemaiciai) by direct sequencing of the first hypervariable segment (HVI) of the control region of mitochondrial DNA (mtDNA) and restriction enzyme digestion for polymorphic site 00073. On the basis of specific nucleotide substitutions the obtained sequences were classified to mtDNA haplogroups. This revealed the presence of almost all European haplogroups (except X) in the Lithuanian sample, including those that expanded through Europe in the Palaeolithic and those whose expansion occurred during the Neolithic. Molecular diversity indices (gene diversity 0.97, nucleotide diversity 0.012 and mean number of pairwise differences 4.5) were within the range usually reported in European populations. No significant differences between Aukstaiciai and Zemaiciai subgroups were found, but some slight differences need further investigation.     

Evolutionary history and phylogeography of the schistosome-vector freshwater snail Biomphalaria glabrata based on nuclear and mitochondrial DNA sequences

The phylogeography of the freshwater snail Biomphalaria glabrata remains poorly known, although this species is the major vector of schistosomiasis in the New World. It was here investigated in South America and the Lesser Antilles, based on partial mitochondrial large ribosomal subunit (16S rDNA) and nuclear internal transcribed spacer-2 (ITS-2) gene sequences. Sampling included 17 populations from a large part of the current geographic range of the species (Brazil, Venezuela and Lesser Antilles). Substantial variability was detected, as well as a high amount of phylogenetically informative signal. The molecular phylogeny inferred splits B. glabrata into Northern and Southern clades separated by the Amazon river, and may even suggest a supra-specific status for B. glabrata. Brazilian populations were the most diverse and appeared basal to the other populations. Venezuelan haplotypes formed a single clade, albeit not strongly supported. Two Venezuelan haplotypes appear rather similar to Brazilian haplotypes. Similarly, Lesser Antilles haplotypes clustered in the same monophyletic clade, which suggests that the recent colonisation of the Antilles has a northern South American origin. However, the estimated divergence time between Antilles and Venezuelan sequences is extremely large (conservatively higher than 10(5) years). These results are discussed in the light of (i) phylogeographic patterns at South American scale, and (ii) recurrent introduction of molluscs, especially in the Antilles, as a consequence of human activities.     

Phylogeography of Aglais urticae (Lepidoptera) based on DNA sequences of the mitochondrial COI gene and control region

Mitochondrial DNA (mtDNA) sequences of the COI gene and the control region were used to examine the genetic population structure of Aglais urticae L. (Lepidoptera) over its entire geographic range, i.e., the Palaearctic. The phylogenetic relationships within and between A. urticae subspecies were determined and patterns of mtDNA divergence and ecological differentiation were compared. High gene flow together with a recent and sudden population expansion characterise the genetic population structure of this species. No geographically induced differentiation was observed, nor were subspecies identified as separate evolutionary units. The discrepancy between the genetic and ecological variation is most likely due to the slower rate of mtDNA evolution compared to ecological differentiation. The control region proved to be a less useful molecular marker for the population genetics and the phylogenetic reconstruction of closely related taxa in A. urticae than it has for other species. The extreme bias in adenine and thymine content (A+T=90.91%) probably renders this region highly susceptible to homoplasy, resulting in a less informative molecular marker.     

Phylogenetic relationships and phylogeography of Hynobius tokyoensis (Amphibia: Caudata) using complete sequences of cytochrome b and control region genes of mitochondrial DNA

Using complete sequences of cytochrome b (cyt b) and control region (CR; D-loop) genes of mitochondrial DNA, we investigated the phylogenetic relationships and phylogeography among populations of the salamander Hynobius tokyoensis in northern Japan. Inclusion of populations from Aichi, Chubu region within Hynobius nebulosus by previous results was confirmed because they formed a clade with H. nebulosus. Monophyly of H. tokyoensis was supported in all trees analyzed, and two clades consistently emerged: clade A from northeastern Kanto (Ibaraki) to southern Tohoku (Fukushima), and clade B from the remaining area south of northern Kanto (Tochigi). These two clades are estimated to have an old history of divergence during the late Pliocene, when the present-day Kanto Plain was under the sea. Within clade B, three haplotypes groups (I-III) are hypothesized to have diverged more recently, i.e., between the early and mid-Pleistocene, probably in relation to glacial events. The ancestral groups I and II were separated at the present-day western Kanto and Boso Peninsula areas, respectively, and subsequently, group II invaded northward to the present-day northern Kanto area and gave rise to group III. Populations of the Miura Peninsula are thought to have multiple origins, one directly from Boso and another from a more recent southward invasion from the northern Kanto area. Cytochrome b appears to have evolved more quickly than CR genes in H. tokyoensis, and thus will be more useful for phylogenetic analyses and formulating conservation measures.     

Origin and evolution of homologous repeated sequences in the mitochondrial DNA control region of shrews

The complete mitochondrial DNA (mtDNA) control region was amplified and directly sequenced in two species of shrew, Crocidura russula and Sorex araneus (Insectivora, Mammalia). The general organization is similar to that found in other mammals: a central conserved region surrounded by two more variable domains. However, we have found in shrews the simultaneous presence of arrays of tandem repeats in potential locations where repeats tend to occur separately in other mammalian species. These locations correspond to regions which are associated with a possible interruption of the replication processes, either at the end of the three-stranded D-loop structure or toward the end of the heavy-strand replication. In the left domain the repeated sequences (R1 repeats) are 78 bp long, whereas in the right domain the repeats are 12 bp long in C. russula and 14 bp long in S. araneus (R2 repeats). Variation in the copy number of these repeated sequences results in mtDNA control region length differences. Southern blot analysis indicates that level of heteroplasmy (more than one mtDNA form within an individual) differs between species. A comparative study of the R2 repeats in 12 additional species representing three shrew subfamilies provides useful indications for the understanding of the origin and the evolution of these homologous tandemly repeated sequences. An asymmetry in the distribution of variants within the arrays, as well as the constant occurrence of shorter repeated sequences flanking only one side of the R2 arrays, could be related to asymmetry in the replication of each strand of the mtDNA molecule. The pattern of sequence and length variation within and between species, together with the capability of the arrays to form stable secondary structures, suggests that the dominant mechanism involved in the evolution of these arrays in unidirectional replication slippage.