Evolutionary characteristics of the mitochondrial NADH dehydrogenase subunit 6 gene in some populations of four sympatric Mustela species (Mustelidae, Mammalia) from central Europe

BACKGROUND

Selection on or reticulate evolution of mtDNA is documented in various mammalian taxa and could lead to misleading phylogenetic conclusions if not recognized. We sequenced the MT-ND6 gene of four sympatric Mustelid species of the genus Mustela from some central European populations. We hypothesised positive selection on MT-ND6, given its functional importance and the different body sizes and life histories of the species, even though climatic differences may be unimportant for adaptation in sympatry.

METHODS AND RESULTS

MT-ND6 genes were sequenced in 187 sympatric specimens of weasels, Mustela nivalis, stoats, M. erminea, polecats, M. putorius, and steppe polecats, M. eversmannii, from eastern Austria and of fourteen allopatric polecats from eastern-central Germany. Median joining networks, neighbour joining and maximum likelihood analyses as well as Bayesian inference grouped all species according to earlier published phylogenetic models. However, polecats and steppe polecats, two very closely related species, shared the same two haplotypes. We found only negative selection within the Mustela sequences, including 131 downloaded ones covering thirteen species. Positive selection was observed on three MT-ND6 codons of other mustelid genera retrieved from GenBank.

CONCLUSIONS

Negative selection for MT-ND6 within the genus Mustela suggests absence of both environmental and species-specific effects of cellular energy metabolism despite large species-specific differences in body size. The presently found shared polymorphism in European polecats and steppe polecats may result from ancestral polymorphism before speciation and historical or recent introgressive hybridization; it may indicate mtDNA capture of steppe polecats by M. putorius in Europe.

Maps of Constitutive-Heterochromatin Distribution for Four Martes Species (Mustelidae, Carnivora, Mammalia) Show the Formative Role of Macrosatellite Repeats in Interspecific Variation of Chromosome Structure

Constitutive-heterochromatin placement in the genome affects chromosome structure by occupying centromeric areas and forming large blocks. To investigate the basis for heterochromatin variation in the genome, we chose a group of species with a conserved euchromatin part: the genus Martes [stone marten (M. foina, 2n = 38), sable (M. zibellina, 2n = 38), pine marten (M. martes, 2n = 38), and yellow-throated marten (M. flavigula, 2n = 40)]. We mined the stone marten genome for the most abundant tandem repeats and selected the top 11 macrosatellite repetitive sequences. Fluorescent in situ hybridization revealed distributions of the tandemly repeated sequences (macrosatellites, telomeric repeats, and ribosomal DNA). We next characterized the AT/GC content of constitutive heterochromatin by CDAG (Chromomycin A3-DAPI-after G-banding). The euchromatin conservatism was shown by comparative chromosome painting with stone marten probes in newly built maps of the sable and pine marten. Thus, for the four Martes species, we mapped three different types of tandemly repeated sequences critical for chromosome structure. Most macrosatellites are shared by the four species with individual patterns of amplification. Some macrosatellites are specific to a species, autosomes, or the X chromosome. The variation of core macrosatellites and their prevalence in a genome are responsible for the species-specific variation of the heterochromatic blocks.

Identification of a new species of Ixodes Latreille, 1795 (Acari: Ixodidae), parasite of hog badgers (Carnivora: Mustelidae) in China

Ixodes hunanensis n. sp. (Acari: Ixodidae), is identified based on the morphological characteristics and molecular biological analyses of males and females ex hog badger, Arctonyx collaris Cuvier (Carnivora: Mustelidae) from China. Adults of this new species are similar to those of other species of the subgenus Pholeoixodes Schulze, 1942, from which they can be distinguished by the shape of basis capituli, development of cornua, size of porose areas, shape, and size of spurs on coxae and phylogenetic analyses of the cox1 and 16S rRNA sequences.

Badger genome grows Tree of Life

Sequencing the genome of the European badger is the latest step in a project to determine the genomes of all species in the UK and beyond. Georgina Mills reports.

Characterisation of the Complete Mitochondrial Genome of Critically Endangered Mustela lutreola (Carnivora: Mustelidae) and Its Phylogenetic and Conservation Implications

In this paper, a complete mitochondrial genome of the critically endangered European mink Mustela lutreola L., 1761 is reported. The mitogenome was 16,504 bp in length and encoded the typical 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes, and harboured a putative control region. The A+T content of the entire genome was 60.06% (A > T > C > G), and the AT-skew and GC-skew were 0.093 and −0.308, respectively. The encoding-strand identity of genes and their order were consistent with a collinear gene order characteristic for vertebrate mitogenomes. The start codons of all protein-coding genes were the typical ATN. In eight cases, they were ended by complete stop codons, while five had incomplete termination codons (TA or T). All tRNAs had a typical cloverleaf secondary structure, except tRNA^Ser(AGC) and tRNA^Lys, which lacked the DHU stem and had reduced DHU loop, respectively. Both rRNAs were capable of folding into complex secondary structures, containing unmatched base pairs. Eighty-one single nucleotide variants (substitutions and indels) were identified. Comparative interspecies analyses confirmed the close phylogenetic relationship of the European mink to the so-called ferret group, clustering the European polecat, the steppe polecat and the black-footed ferret. The obtained results are expected to provide useful molecular data, informing and supporting effective conservation measures to save M. lutreola.

Comparative transcriptome analysis revealed omnivorous adaptation of the small intestine of Melinae

As the main digestive organ, the small intestine plays a vital role in the digestion of animals. At present, most of the research on animal feeding habits focuses on carnivores and herbivores. However, the mechanism of feeding and digestion in omnivores remains unclear. This study aims to reveal the molecular basis of the omnivorous adaptive evolution of Melinae by comparing the transcriptome of the small intestines of Asian Badgers (Meles leucurus) and Northern Hog Badgers (Arctonyx albogularis). We obtained high-quality small intestinal transcriptome data from these two species. Key genes and signalling pathways were analysed through Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and other databases. Research has mainly found that orthologous genes related to six enzymes have undergone adaptive evolution. In addition, the study also found three digestion-related pathways (cGMP-PKG, cAMP, and Hippo). They are related to the digestion and absorption of nutrients, the secretion of intestinal fluids, and the transport of food through the small intestine, which may help omnivorous animals adapt to an omnivorous diet. Our study provides insight into the adaptation of Melinae to omnivores and affords a valuable transcriptome resource for future research.

Prevalence of Campylobacter spp. in Raccoon Dogs and Badgers in Miyazaki Prefecture, Japan

A total of 55 samples of intestinal contents from 28 raccoon dogs (Nyctereutes procyonoides) and 27 badgers (Males anakuma) in Miyazaki prefecture, Japan, were examined for the presence of Campylobacter species. C. jejuni and C. upsaliensis were isolated from 3.6% (n = 1) and 75% (n = 21) of raccoon dogs, respectively. In contrast, no Campylobacter spp. was isolated from the badgers examined. The C. upsaliensis isolates were subjected to antimicrobial susceptibility testing against 8 antimicrobial agents. This revealed that most of the isolates from raccoon dogs were susceptible to the antimicrobial agents examined, whereas strains isolated from healthy dogs in Miyazaki prefecture, showed high rates of resistance. Virulence genes (flaA, cadF, ciaB, cdtA, cdtB, and cdtC) were present in the C. jejuni isolate from a raccoon dog, with the exception of flaB. By contrast, all these virulence genes examined were present in all C. upsaliensis strains isolated from raccoon dogs and dogs. The genetic diversity of those isolates based on the nucleotide sequences of 7 housekeeping genes (adk, aspA, atpA, glnA, glyA, pgi, tkt) was compared with that of C. upsaliensis strains isolated from dogs and strains selected randomly from humans and dogs deposited in the Campylobacter MLST database. The major cluster of raccoon dog strains was separated from both human and dog strains by phylogenetic tree analysis. These results suggest that raccoon dogs are a reservoir of C. upsaliensis and that isolates may represent a population different from that in humans and dogs. To our knowledge, this is the first study to have demonstrated a high prevalence of C. upsaliensis in raccoon dogs.

First Draft Genome of the Sable, Martes zibellina

Members of genus Martes provide early warning signals about forest ecosystem health and are designated as a Management Indicator Species. As one of the most widespread members in Martes, the sable (Martes zibellina) is a circumboreal small predator found throughout all taiga zoogeographical zones of Eurasia and shows distinct population differentiation and morphological variations. To support further studies on striking local adaptation and population evolution, we present the first sable genome, assembled de novo from an individual originating in the Great Khingan Mountains (China). The assembled genome is 2.42 Gb, consisting of 15,814 scaffolds with a scaffold N50 of 5.20 Mb. Searches for complete Mammalia BUSCO (Benchmarking Universal Single-Copy Ortholog) gene groups found that 95.15% of the curated single-copy orthologs were assembled as complete, suggesting a high level of completeness of the genome. We totally predicted 19,413 protein-coding genes, and 0.82 Gb of repeat sequences was annotated. We also detected 1,257 olfactory receptor genes and found more functional olfactory receptor genes in sable than in other Mustelidae species, which provide a possible genetic explanation for the acute sense of smell of the sable for searching the preys under deep snow. Phylogenetic analyses revealed that the ferret (Mustela putorius furo) and sea otter (Enhydra lutris) form a clade that is sister to the sable, which was dated ∼16.4 Ma. Overall, our study provided the first reference genome for research in a broad range of areas including local adaptations, population evolution, conservation, and management for sable.

The Results of Sable (Martes zibellina) Reintroduction Demonstrate the Founder Effect

The relative abundance of intrapopulation groups with different parameters of skull size, coat color, and expression of an epigenetic cranial trait was compared in autochthonous, reintroduced, and donor populations of sable. Recovery of the species resources and broad variability of the phenotypic trait complex in the newly fomned populations were observed. A large proportion of the animals had the phenotype that included large size, dark coat color, and pronounced expression of a specific phene trait (foramen in the condylar fossa) and was not characteristic of the neighboring autochthonous populations. It is reasonable to attribute the presence of individuals with an unusual morphology in the newly formed populations of animals to a manifestation of the founder principle, because the effect of this principle was promoted by spatial isolation of the primary foci of translocated animals.

No Compensatory Relationship between the Innate and Adaptive Immune System in Wild-Living European Badgers

The innate immune system provides the primary vertebrate defence system against pathogen invasion, but it is energetically costly and can have immune pathological effects. A previous study in sticklebacks found that intermediate major histocompatibility complex (MHC) diversity correlated with a lower leukocyte coping capacity (LCC), compared to individuals with fewer, or many, MHC alleles. The organization of the MHC genes in mammals, however, differs to the highly duplicated MHC genes in sticklebacks by having far fewer loci. Using European badgers (Meles meles), we therefore investigated whether innate immune activity, estimated functionally as the ability of an individual’s leukocytes to produce a respiratory burst, was influenced by MHC diversity. We also investigated whether LCC was influenced by factors such as age-class, sex, body condition, season, year, neutrophil and lymphocyte counts, and intensity of infection with five different pathogens. We found that LCC was not associated with specific MHC haplotypes, MHC alleles, or MHC diversity, indicating that the innate immune system did not compensate for the adaptive immune system even when there were susceptible MHC alleles/haplotypes, or when the MHC diversity was low. We also identified a seasonal and annual variation of LCC. This temporal variation of innate immunity was potentially due to physiological trade-offs or temporal variation in pathogen infections. The innate immunity, estimated as LCC, does not compensate for MHC diversity suggests that the immune system may function differently between vertebrates with different MHC organizations, with implications for the evolution of immune systems in different taxa.

The complete mitochondrial genome sequence of Neovison vison (Carnivora: Mustelidae)

The phylogenetic and taxonomic position of the American mink Neovison vison have long been unclear. In this paper, the complete mitogenome of N. vison was sequenced and characterized. The total length was 16,594 bp and typically consists of 37 genes, including 13 protein-coding genes, 2 rRNAs, 22 tRNA, a large control region (CR) and a light-strand replication origin (OL). Gene contents, locations, and arrangements were identical to those of typical vertebrate. The overall base composition is 33.6%, 25.4%, 27.8% and 13.3% for A, C, T and G, respectively, with a moderate bias on AT content (61.4%). This result is expected to provide useful molecular data and contribute to further taxonomic and phylogenetic studies of Mustelidae and Carnivora.

The Ancestral Carnivore Karyotype As Substantiated by Comparative Chromosome Painting of Three Pinnipeds, the Walrus, the Steller Sea Lion and the Baikal Seal (Pinnipedia, Carnivora)

Karyotype evolution in Carnivora is thoroughly studied by classical and molecular cytogenetics and supplemented by reconstructions of Ancestral Carnivora Karyotype (ACK). However chromosome painting information from two pinniped families (Odobenidae and Otariidae) is noticeably missing. We report on the construction of the comparative chromosome map for species from each of the three pinniped families: the walrus (Odobenus rosmarus, Odobenidae–monotypic family), near threatened Steller sea lion (Eumetopias jubatus, Otariidae) and the endemic Baikal seal (Pusa sibirica, Phocidae) using combination of human, domestic dog and stone marten whole-chromosome painting probes. The earliest karyological studies of Pinnipedia showed that pinnipeds were characterized by a pronounced karyological conservatism that is confirmed here with species from Phocidae, Otariidae and Odobenidae sharing same low number of conserved human autosomal segments (32). Chromosome painting in Pinnipedia and comparison with non-pinniped carnivore karyotypes provide strong support for refined structure of ACK with 2n = 38. Constructed comparative chromosome maps show that pinniped karyotype evolution was characterized by few tandem fusions, seemingly absent inversions and slow rate of genome rearrangements (less then one rearrangement per 10 million years). Integrative comparative analyses with published chromosome painting of Phoca vitulina revealed common cytogenetic signature for Phoca/Pusa branch and supports Phocidae and Otaroidea (Otariidae/Odobenidae) as sister groups. We revealed rearrangements specific for walrus karyotype and found the chromosomal signature linking together families Otariidae and Odobenidae. The Steller sea lion karyotype is the most conserved among three studied species and differs from the ACK by single fusion. The study underlined the strikingly slow karyotype evolution of the Pinnipedia in general and the Otariidae in particular.

Fine-scale landscape genetics of the American badger (Taxidea taxus): disentangling landscape effects and sampling artifacts in a poorly understood species

Landscape genetics is a powerful tool for conservation because it identifies landscape features that are important for maintaining genetic connectivity between populations within heterogeneous landscapes. However, using landscape genetics in poorly understood species presents a number of challenges, namely, limited life history information for the focal population and spatially biased sampling. Both obstacles can reduce power in statistics, particularly in individual-based studies. In this study, we genotyped 233 American badgers in Wisconsin at 12 microsatellite loci to identify alternative statistical approaches that can be applied to poorly understood species in an individual-based framework. Badgers are protected in Wisconsin owing to an overall lack in life history information, so our study utilized partial redundancy analysis (RDA) and spatially lagged regressions to quantify how three landscape factors (Wisconsin River, Ecoregions and land cover) impacted gene flow. We also performed simulations to quantify errors created by spatially biased sampling. Statistical analyses first found that geographic distance was an important influence on gene flow, mainly driven by fine-scale positive spatial autocorrelations. After controlling for geographic distance, both RDA and regressions found that Wisconsin River and Agriculture were correlated with genetic differentiation. However, only Agriculture had an acceptable type I error rate (3-5%) to be considered biologically relevant. Collectively, this study highlights the benefits of combining robust statistics and error assessment via simulations and provides a method for hypothesis testing in individual-based landscape genetics.

[Mitochondrial Genome Variability in the Wolverine (Gulo gulo)]

The nucleotide sequence of an extended mitochondrial genome segment (11473 base pairs in size) was determined in the wolverine (Gulo gulo) from Magadan oblast. Phylogenetic and statistical analyses of mitochondrial DNA (mtDNA) sequences of mustelids showed that the separation of the Gulo phylogenetic branch occurred at the Miocene--early Pliocene (about 5.6 million years ago (MYA)), while the formation of the species G. gulo took place in the Middle Pleistocene (181 and 234 thousand years ago (KYA), according to the results of molecular dating based on the variability of the extended mtDNA segment and the mitochondrial cytochrome b gene, respectively). The molecular data were in agreement with the fossil records for wolverines.

[Topological Conflicts in Phylogenetic Analysis of Different Regions of the Sable (Martes zibellina L.) Mitochondrial Genome]

Phylogenetic analysis of different regions of the mitochondrial genome of the sable showed the presence of several topologies of phylogenetic trees, but the most statistically significant topology is A-BC, which was obtained as a result of the analysis of the mitochondrial genome as a whole, as well as of the individual CO1, ND4, and ND5 genes. Analysis of the intergroup divergence of the mtDNA haplotypes (Dxy) indicated that the maximum Dxy values between A and BC groups were accompanied by minimum differences between B and C groups only for six genes showing the A-BC topology (12S rRNA; CO1, CO2, ND4, ND5, and CYTB). It is assumed that the topological conflicts observed in the analysis of individual sable mtDNA genes are associated with the uneven distribution of mutations along the mitochondrial genome and the mitochondrial tree. This may be due to random causes, as well as the nonuniform effect of selection.

Inferring Population Genetic Structure in Widely and Continuously Distributed Carnivores: The Stone Marten (Martes foina) as a Case Study

The stone marten is a widely distributed mustelid in the Palaearctic region that exhibits variable habitat preferences in different parts of its range. The species is a Holocene immigrant from southwest Asia which, according to fossil remains, followed the expansion of the Neolithic farming cultures into Europe and possibly colonized the Iberian Peninsula during the Early Neolithic (ca. 7,000 years BP). However, the population genetic structure and historical biogeography of this generalist carnivore remains essentially unknown. In this study we have combined mitochondrial DNA (mtDNA) sequencing (621 bp) and microsatellite genotyping (23 polymorphic markers) to infer the population genetic structure of the stone marten within the Iberian Peninsula. The mtDNA data revealed low haplotype and nucleotide diversities and a lack of phylogeographic structure, most likely due to a recent colonization of the Iberian Peninsula by a few mtDNA lineages during the Early Neolithic. The microsatellite data set was analysed with a) spatial and non-spatial Bayesian individual-based clustering (IBC) approaches (STRUCTURE, TESS, BAPS and GENELAND), and b) multivariate methods [discriminant analysis of principal components (DAPC) and spatial principal component analysis (sPCA)]. Additionally, because isolation by distance (IBD) is a common spatial genetic pattern in mobile and continuously distributed species and it may represent a challenge to the performance of the above methods, the microsatellite data set was tested for its presence. Overall, the genetic structure of the stone marten in the Iberian Peninsula was characterized by a NE-SW spatial pattern of IBD, and this may explain the observed disagreement between clustering solutions obtained by the different IBC methods. However, there was significant indication for contemporary genetic structuring, albeit weak, into at least three different subpopulations. The detected subdivision could be attributed to the influence of the rivers Ebro, Tagus and Guadiana, suggesting that main watercourses in the Iberian Peninsula may act as semi-permeable barriers to gene flow in stone martens. To our knowledge, this is the first phylogeographic and population genetic study of the species at a broad regional scale. We also wanted to make the case for the importance and benefits of using and comparing multiple different clustering and multivariate methods in spatial genetic analyses of mobile and continuously distributed species.

[Geographical structure of the sable (Martes zibellina L.) gene pool on the basis of microsatellite loci analysis]

The genetic structure of seven natural sable populations was investigated with the use of the original panel of 10 microsatellite loci. The populations were selected on the basis of the historical data on sable numbers fluctuations for the last 300 years, as well as on data on natural and artificial migrations affecting neighboring populations. We have demonstrated that the populations are in a state of genetic equilibrium for the majority of the loci. The genetic differences between three samplings from Central Siberia populations were insignificant, and the fixation index values were relatively low. At the same time, populations from the margins of the species habitation areal were characterized by the highest fixation index values. We have shown for the first time that populations from different regions of the sable habitation areal maintain their specific features despite the influence of natural and artificial migrations. The current study, performed with nuclear genetic markers, made it possible to get insight into the genetic structure of the analyzed species as a whole.

Revisiting the phylogeography and demography of European badgers (Meles meles) based on broad sampling, multiple markers and simulations

Although the phylogeography of European mammals has been extensively investigated since the 1990s, many studies were limited in terms of sampling distribution, the number of molecular markers used and the analytical techniques employed, frequently leading to incomplete postglacial recolonisation scenarios. The broad-scale genetic structure of the European badger (Meles meles) is of interest as it may result from historic restriction to glacial refugia and/or recent anthropogenic impact. However, previous studies were based mostly on samples from western Europe, making it difficult to draw robust conclusions about the location of refugia, patterns of postglacial expansion and recent demography. In the present study, continent-wide sampling and analyses with multiple markers provided evidence for two glacial refugia (Iberia and southeast Europe) that contributed to the genetic variation observed in badgers in Europe today. Approximate Bayesian computation provided support for a colonisation of Scandinavia from both Iberian and southeastern refugia. In the whole of Europe, we observed a decline in genetic diversity with increasing latitude, suggesting that the reduced diversity in the peripheral populations resulted from a postglacial expansion processes. Although MSVAR v.1.3 also provided evidence for recent genetic bottlenecks in some of these peripheral populations, the simulations performed to estimate the method's power to correctly infer the past demography of our empirical populations suggested that the timing and severity of bottlenecks could not be established with certainty. We urge caution against trying to relate demographic declines inferred using MSVAR with particular historic or climatological events.

Landscape genetics for the empirical assessment of resistance surfaces: the European pine marten (Martes martes) as a target-species of a regional ecological network

Coherent ecological networks (EN) composed of core areas linked by ecological corridors are being developed worldwide with the goal of promoting landscape connectivity and biodiversity conservation. However, empirical assessment of the performance of EN designs is critical to evaluate the utility of these networks to mitigate effects of habitat loss and fragmentation. Landscape genetics provides a particularly valuable framework to address the question of functional connectivity by providing a direct means to investigate the effects of landscape structure on gene flow. The goals of this study are (1) to evaluate the landscape features that drive gene flow of an EN target species (European pine marten), and (2) evaluate the optimality of a regional EN design in providing connectivity for this species within the Basque Country (North Spain). Using partial Mantel tests in a reciprocal causal modeling framework we competed 59 alternative models, including isolation by distance and the regional EN. Our analysis indicated that the regional EN was among the most supported resistance models for the pine marten, but was not the best supported model. Gene flow of pine marten in northern Spain is facilitated by natural vegetation, and is resisted by anthropogenic landcover types and roads. Our results suggest that the regional EN design being implemented in the Basque Country will effectively facilitate gene flow of forest dwelling species at regional scale.

Neighbouring-group composition and within-group relatedness drive extra-group paternity rate in the European badger (Meles meles)

Extra-group paternity (EGP) occurs commonly among group-living mammals and plays an important role in mating systems and the dynamics of sexual selection; however, socio-ecological and genetic correlates of EGP have been underexplored. We use 23 years of demographic and genetic data from a high-density European badger (Meles meles) population, to investigate the relationship between the rate of EGP in litters and mate availability, mate incompatibility and mate quality (heterozygosity). Relatedness between within-group assigned mothers and candidate fathers had a negative quadratic effect on EGP, whereas the number of neighbouring-group candidate fathers had a linear positive effect. We detected no effect of mean or maximum heterozygosity of within-group candidate fathers on EGP. Consequently, EGP was associated primarily with mate availability, subject to within-group genetic effects, potentially to mitigate mate incompatibility and inbreeding. In badgers, cryptic female choice, facilitated by superfecundation, superfoetation and delayed implantation, prevents males from monopolizing within-group females. This resonates with a meta-analysis in group-living mammals, which proposed that higher rates of EGP occur when within-group males cannot monopolize within-group females. In contrast to the positive meta-analytic association, however, we found that EGP associated negatively with the number of within-group assigned mothers and the number of within-group candidate fathers; potentially a strategy to counter within-group males committing infanticide. The relationship between the rate of EGP and socio-ecological or genetic factors can therefore be intricate, and the potential for cryptic female choice must be accounted for in comparative studies.

Age-related declines and disease-associated variation in immune cell telomere length in a wild mammal

Immunosenescence, the deterioration of immune system capability with age, may play a key role in mediating age-related declines in whole-organism performance, but the mechanisms that underpin immunosenescence are poorly understood. Biomedical research on humans and laboratory models has documented age and disease related declines in the telomere lengths of leukocytes ('immune cells'), stimulating interest their having a potentially general role in the emergence of immunosenescent phenotypes. However, it is unknown whether such observations generalise to the immune cell populations of wild vertebrates living under ecologically realistic conditions. Here we examine longitudinal changes in the mean telomere lengths of immune cells in wild European badgers (Meles meles). Our findings provide the first evidence of within-individual age-related declines in immune cell telomere lengths in a wild vertebrate. That the rate of age-related decline in telomere length appears to be steeper within individuals than at the overall population level raises the possibility that individuals with short immune cell telomeres and/or higher rates of immune cell telomere attrition may be selectively lost from this population. We also report evidence suggestive of associations between immune cell telomere length and bovine tuberculosis infection status, with individuals detected at the most advanced stage of infection tending to have shorter immune cell telomeres than disease positive individuals. While male European badgers are larger and show higher rates of annual mortality than females, we found no evidence of a sex difference in either mean telomere length or the average rate of within-individual telomere attrition with age. Our findings lend support to the view that age-related declines in the telomere lengths of immune cells may provide one potentially general mechanism underpinning age-related declines in immunocompetence in natural populations.

[Genetic variability of sable Martes zibellina L., pine marten M. martes L., and their hybrids in Western Siberia: protein and DNA polymorphism]

Using four types of markers, the genetic variability of sable and pine marten inhabiting Western Siberia was examined. Izoenzyme and restriction endonuclease analysis of the mtDNA cytochrome b gene fragment, as well as the ISSR-PCR and analysis of microsatellite variation, revealed a low differentiation level of sable and pine marten and confirmed the hybrid origin of atypical representatives of these species. The hybrids were characterized by an increased heterozygosity level and were genetically closer to sable than to pine marten. In atypical martens, the presence of mtDNA haplotypes of eastern sable was identified. This could be the consequence of the reintroduction of the Barguzin sable in the 20th century. In Western Siberia, the introgression of genes between sable and pine marten was massive and symmetrical. It apparently occurred in the past and continues in the present.

Phylogeography and post-glacial recolonization in wolverines (Gulo gulo) from across their circumpolar distribution

Interglacial-glacial cycles of the Quaternary are widely recognized in shaping phylogeographic structure. Patterns from cold adapted species can be especially informative - in particular, uncovering additional glacial refugia, identifying likely recolonization patterns, and increasing our understanding of species' responses to climate change. We investigated phylogenetic structure of the wolverine, a wide-ranging cold adapted carnivore, using a 318 bp of the mitochondrial DNA control region for 983 wolverines (n=209 this study, n=774 from GenBank) from across their full Holarctic distribution. Bayesian phylogenetic tree reconstruction and the distribution of observed pairwise haplotype differences (mismatch distribution) provided evidence of a single rapid population expansion across the wolverine's Holarctic range. Even though molecular evidence corroborated a single refugium, significant subdivisions of population genetic structure (0.01< ΦST <0.99, P<0.05) were detected. Pairwise ΦST estimates separated Scandinavia from Russia and Mongolia, and identified five main divisions within North America - the Central Arctic, a western region, an eastern region consisting of Ontario and Quebec/Labrador, Manitoba, and California. These data are in contrast to the nearly panmictic structure observed in northwestern North America using nuclear microsatellites, but largely support the nuclear DNA separation of contemporary Manitoba and Ontario wolverines from northern populations. Historic samples (c. 1900) from the functionally extirpated eastern population of Quebec/Labrador displayed genetic similarities to contemporary Ontario wolverines. To understand these divergence patterns, four hypotheses were tested using Approximate Bayesian Computation (ABC). The most supported hypothesis was a single Beringia incursion during the last glacial maximum that established the northwestern population, followed by a west-to-east colonization during the Holocene. This pattern is suggestive of colonization occurring in accordance with glacial retreat, and supports expansion from a single refugium. These data are significant relative to current discussions on the conservation status of this species across its range.

The sensitivity of genetic connectivity measures to unsampled and under-sampled sites

Landscape genetic analyses assess the influence of landscape structure on genetic differentiation. It is rarely possible to collect genetic samples from all individuals on the landscape and thus it is important to assess the sensitivity of landscape genetic analyses to the effects of unsampled and under-sampled sites. Network-based measures of genetic distance, such as conditional genetic distance (cGD), might be particularly sensitive to sampling intensity because pairwise estimates are relative to the entire network. We addressed this question by subsampling microsatellite data from two empirical datasets. We found that pairwise estimates of cGD were sensitive to both unsampled and under-sampled sites, and F_ST, D_est, and d_eucl were more sensitive to under-sampled than unsampled sites. We found that the rank order of cGD was also sensitive to unsampled and under-sampled sites, but not enough to affect the outcome of Mantel tests for isolation by distance. We simulated isolation by resistance and found that although cGD estimates were sensitive to unsampled sites, by increasing the number of sites sampled the accuracy of conclusions drawn from landscape genetic analyses increased, a feature that is not possible with pairwise estimates of genetic differentiation such as F_ST, D_est, and d_eucl. We suggest that users of cGD assess the sensitivity of this measure by subsampling within their own network and use caution when making extrapolations beyond their sampled network.

[Genetic structure of sable (Martes zibellina L.) from Eurasia based on distribution of mitochondrial lineages]

The phylogeography of the sable, which is a commercially valuable species, is extremely complicated and poorly investigated. Specifically, the effects of factors such as the range dynamics of the sable during the Pleistocene Epoch, the localization of glacial refugia, species distribution pattern in Holocene, and recent dramatic population decline, along with massive reacclimatization measures, on the species phylogeography remain unclear. Based on the sequence analysis of the control region of mitochondrial DNA from sables that inhabit different parts of the species range, a suggestion was made of the considerably high Pleistocene genetic diversity in sable, which was subsequently lost. The initial diversity of mitochondrial lineages is mostly preserved in the Urals, while in the eastern part of the range, it seems to have been depleted as early as before the last glacial maximum. On the other hand, the even greater depletion of the mitochondrial lineages observed in some populations of central Siberia can be associated with the dramatic population decline at the turn of the 20th century.

[Population aspects of sexual dimorphism in guild of the Mustelidae: Mustela lutreola, Neovison vison, Mustela putorius, Martes martes as an example]

Size sexual dimorphism was investigated on 695 skulls of four Mustelidae species. By extent of increasing of differences between sexes the species are placed in following order: European pine marten (Martes martes), European mink (Mustela lutreola), American mink (Neovison vison), and European polecat (Mustela putorius). Extent of the dimorphism characterizes ecological plasticity of the species and is population characteristic. It is shown that M. martes takes specific and relatively narrow ecological niche of forest ecosystems, entering into weak competitive relationships with smaller Mustelidae species. The level of sexual dimorphism of M. lutreola, N. vison and M. putorius reflects intensity of its interspecific relationships within study area. High level of sexual dimorphism of M. putorius is determined by further divergence of ecological niches of males and females, and also appears to be compensatory mechanism reducing consequences of hardened environmental requirements.

[The mountain weasel Mustela kathiah (Carnivora: Mustelidae): molecular and karyological data]

The karyotype of Mustela kathiah was first described. Its structure is most similar to the karyotype of M. altaica, differing inthe morphological peculiarites of five pairs of large chromosomes. A comparative analysis of mitochondrial genes in the species Mustela allowed us to clarify understanding of the place of M. kathiah in the system of the genus. The earlier hypothesized proximity of the species to a group of small weasels (altaica, nivalis) or to a group of South Asian species (strigidorsa, nudipes) was not confirmed. A high level of differences between M. kathiah of Vietnam and specimens from southern China in nucleotide sequences of the cytochrome b (7.7%) and ND2 (6-6.2%) genes was found. Perhaps these differences, manifested in populations of M. kathiah from different regions, are adaptive.

Historical and contemporary DNA indicate fisher decline and isolation occurred prior to the European settlement of California

Establishing if species contractions were the result of natural phenomena or human induced landscape changes is essential for managing natural populations. Fishers (Martes pennanti) in California occur in two geographically and genetically isolated populations in the northwestern mountains and southern Sierra Nevada. Their isolation is hypothesized to have resulted from a decline in abundance and distribution associated with European settlement in the 1800s. However, there is little evidence to establish that fisher occupied the area between the two extant populations at that time. We analyzed 10 microsatellite loci from 275 contemporary and 21 historical fisher samples (1880-1920) to evaluate the demographic history of fisher in California. We did not find any evidence of a recent (post-European) bottleneck in the northwestern population. In the southern Sierra Nevada, genetic subdivision within the population strongly influenced bottleneck tests. After accounting for genetic subdivision, we found a bottleneck signal only in the northern and central portions of the southern Sierra Nevada, indicating that the southernmost tip of these mountains may have acted as a refugium for fisher during the anthropogenic changes of the late 19(th) and early 20(th) centuries. Using a coalescent-based Bayesian analysis, we detected a 90% decline in effective population size and dated the time of decline to over a thousand years ago. We hypothesize that fisher distribution in California contracted to the two current population areas pre-European settlement, and that portions of the southern Sierra Nevada subsequently experienced another more recent bottleneck post-European settlement.

[Mitochondrial genome variation in domesticated sable (Martes zibellina)]

The first comparison of mitochondrial variations in sables from captive and natural populations of the Urals, Central Siberia, Yakutia, Kamchatka, and Japan has been performed. The object of comparative analysis was a 427-bp 5' fragment of the mitochondrial control region, including the D-loop. Two main haplogroups of the sable mitochondrial genome have been found, which provides new data for reconstruction of the spread of the sable over its current range. Asymmetry of the haplotype abundances in the captive populations of sables has been detected. The mitochondrial haplotypes characteristic of sable breeds have been identified. The possible role of the frequent mitochondrial haplotypes of the captive population in the sable adaptation to the conditions of captivity is discussed.

[Microsatellite analysis of two captive populations of sable (Martes zibellina L.)]

The high value of sable (Martes zibellina L.) fur and stable demand for it over the centuries have led to suboptimal hunting patterns and, as a result, considerable fluctuations in the sizes of natural populations of this species. To maintain the traditional export of sable fur, efforts towards commercial domestication of sable have been made in Russia. The first farm population of sable consisted of animal from eight natural populations in 1929. After the problems related to breeding in captivity were solved, directional selection began. Eighty years of breeding have resulted in sable herds with homogeneous quantitative characters. Prospects for further breeding depend on the current level of genetic diversity in the captive populations of sables formed during the first stages of domestication. The sable populations of the Pushkinsky and Saltykovsky fur farms located in Moscow oblast, which were the objects of this study, are the progenitors of the existing captive populations. The first estimation of genetic variation of this species by means of a panel of microsatellite markers was developed for this study. Two captive sable populations were analyzed using ten microsatellite loci; a total of 75 alleles were found in both populations. Population-specific alleles were identified (6 and 13 in the Pushkinsky and Saltykovsky populations, respectively). The populations studied were found to be differentiated with respect to four microsatellite loci.

[Adaptive intraspecific divergence: an example using the animal cytochrome b gene]

The topologies of phylogenetic trees characterized by a high level of intraspecific divergence between the phylogenetic DNA groups (clades) are often explained in terms of the theory of Pleistocene refugia. To elucidate the issue of the adaptive role of intraspecific divergence, the changes in the physicochemical properties of amino acids in the course ofcladogenesis (MM01 model of the TreeSAAP 3.2 package) were analyzed in this work using as an example the nucleotide sequences of the cytochrome b gene in some species of northern animals (lemmings, redbacked voles, chipmunks, flying squirrels, ermines). It was shown that the process of intraspecific divergence was rarely accompanied by radical amino acid substitutions in cytochrome b caused by adaptation (directional selection). In connection with this, the hypothesis is discussed according to which the adaptive variants formed in the species at the peak of cold were lost with climatic warming due to the drift or selection against individuals adapted to cold.

On the phylogeny of Mustelidae subfamilies: analysis of seventeen nuclear non-coding loci and mitochondrial complete genomes

BACKGROUND

Mustelidae, as the largest and most-diverse family of order Carnivora, comprises eight subfamilies. Phylogenetic relationships among these Mustelidae subfamilies remain argumentative subjects in recent years. One of the main reasons is that the mustelids represent a typical example of rapid evolutionary radiation and recent speciation event. Prior investigation has been concentrated on the application of different mitochondrial (mt) sequence and nuclear protein-coding data, herein we employ 17 nuclear non-coding loci (>15 kb), in conjunction with mt complete genome data (>16 kb), to clarify these enigmatic problems.

RESULTS

The combined nuclear intron and mt genome analyses both robustly support that Taxidiinae diverged first, followed by Melinae. Lutrinae and Mustelinae are grouped together in all analyses with strong supports. The position of Helictidinae, however, is enigmatic because the mt genome analysis places it to the clade uniting Lutrinae and Mustelinae, whereas the nuclear intron analysis favors a novel view supporting a closer relationship of Helictidinae to Martinae. This finding emphasizes a need to add more data and include more taxa to resolve this problem. In addition, the molecular dating provides insights into the time scale of the origin and diversification of the Mustelidae subfamilies. Finally, the phylogenetic performances and limits of nuclear introns and mt genes are discussed in the context of Mustelidae phylogeny.

CONCLUSION

Our study not only brings new perspectives on the previously obscured phylogenetic relationships among Mustelidae subfamilies, but also provides another example demonstrating the effectiveness of nuclear non-coding loci for reconstructing evolutionary histories in a group that has undergone rapid bursts of speciation.

[Genetic analysis of sympatric sable (Martes zibellina) and Marten (M. martes) populations in the northern urals]

Analysis of nucleotide sequences of the mitochondrial DNA (mtDNA) control region (495 bp) of sables (Martes zibellina) and martens (M. martes) from allopatric parts of the species ranges has shown a considerable interspecific genetic distance (3%). In sympatric populations of these species in the northern Urals, differences between two species-specific mtDNA lineages are still large; however, classification of each individual nucleotide sequence with one of the two lineages is not correlated with whether the given animal is phenotypically a sable, a marten, or a potential hybrid (the so-called kidas). This indicates a high degree of mutual introgression of the sable and marten mtDNAs in the northern Urals and suggests that their interspecific hybridization is common in the sympatric zone.

[Intraspecific structure of sable Martes zibellina inferred from nucleotide variation of the mitochondrial DNA cytochrome b gene]

A fragment of the mitochondrial DNA (mtDNA) cytochrome b gene was sequences in sable from Magadan oblast, Khabarovsk krai, and Kamchatka. Using phylogenetic analysis, the presence of two clusters (A and BC), with the divergence value of 1.4%, was demonstrated. Analysis of the cytochrome b gene median networks indicated that split of the ancestral population took place in early Pleistocene (about one Myr ago), while expansion of its more young phylogenetic group A occurred in late Pleistocene, about 120,000 years ago.

[Toward exploration of morphological disparity of measurable traits of mammalian skull. 3. Distance-based analysis of the morphospace volume and occupation]

Under consideration is a numerical approach to analysis of morphospace volume and occupation based on calculation of Euclidian distances among specimens. The approach, unlike the one of M. Foot (1996), presumes consideration of inter-group distances as one of the morphospace subspaces and definition of the entire morphospace as a totality of both within and between group differences. The subspaces overlap, as a part of morphospace occupation, is defined as a ratio of the volumes of all subspaces to the entire morphospace volume. In calculation of the morphospace specific (relative) volume, the dimension of respective distance matrix is defined as including number of subgroups recognized. The following indices (number of characters being equal and they are preliminary standartized) are suggested to evaluate specific volumes of entire morphospace MD, its k-th subspace PDk, inter-group dissimilarity subspace ID, and subspaces overlap OD: MD = 2sigma(d)/[N(N - K)], PDk = 2sigma(k)d/[n(k)(n(k) - 1)], ID = 2(MD - sigmaPD(k))/[N(N - K) - sigma(k)(n(k) - 1)], OD = K(-1)(ID + sigma(k)PD(k) - MD)/MD, where d is Euclidian distance between any pair of specimens in the entire group, N is number of specimens in that group, K is number of its subgroups, n(k) is number of specimens in k-th subgroup. It is shown that estimates of portions of sex and age differences in the overall disparity obtained by the above distance based method are similar to those derived by the variances component analysis. Bootstrap is shown to provide biased estimates of confidence intervals for the above indices, which is caused by the mathematical properties of the method and not by intrinsic properties of the morphospace. Applications of the approach under consideration are illustrated by analysis of sex and age variaiton of craniometrical traits of the pine marten and the polar fox.

[Changes in correlations between commercially valuable characters of the sable Martes zibellina L. during artificial selection]

A farm population of the sable Martes zibellina L. has been selected for darker coat color during 40 years. Correlations between fitness characters and correlations of these characters with the selected character have been monitored. Correlation analysis has shown that the female fertility in the first year of reproduction is a promising predictor of how valuable the female will be for further breeding. Artificial directional selection has been shown to change the correlations that have been formed in natural populations of the sable. The relationship of this phenomenon with a decrease in the overall fitness during selection that has been observed in the sable population is discussed.

[The effect of artificial selection for coat color on fitness in a farm population of the sable (Martes zibellina)]

The relationship between the response to artificial selection for darker coat color and fitness in a farm population of the sable (Martes zibellina L.) from the Pushkinskoe Fur Farm (Moscow oblast) was studied. The selection was performed during 41 years. By the moment of the study, a response to the selection for this character had been obtained: the coat color in the selected population had become darker, and the proportion of black animals in it increased. In addition, sables with black heads, which were absent in the original population, had appeared. Artificial selection was accompanied by a decrease in the fitness of the selected population, which was expressed in decreased female reproductive capacity parameters (the fertility, maturation rate, and duration of the reproductive period). A selection technique consisting in the use of only highly fertile animals in the selection originally made it possible to restore the fitness parameters to the initial level almost without a decrease in the dark shade of the fur. However, further selection led to a drastic decrease in fitness that could not be precluded by any selection method used. The possible ways to overcome this unfavorable effect of artificial selection are discussed.

[Effect of coat color mutations on behavioral polymorphism in farm populations of american minks (Mustela vison Schreber, 1777) and sables (Martes zibellina Linnaeus, 1758)]

Behavioral polymorphism estimated by the expression of the defensive reaction towards humans has been studied in farm-bred American minks and sables with different color types. Most animals (both minks and sables) from farm populations displayed passive defensive behavior towards humans in the standard hand catch test. Coat color genes have been found to have pleiotropic effects; they influence both the penetrance and expressivity of domestication behavior: in animals with aberrant color types (both sapphire minks and white-and-black sables), the proportion of animals with domestication behavior and the expressivity of this behavior are significantly higher (p <0.01 and p < 0.001, respectively).

Stoats (Mustela erminea) provide evidence of natural overland colonization of Ireland

The current Irish biota has controversial origins. Ireland was largely covered by ice at the Last Glacial Maximum (LGM) and may not have had land connections to continental Europe and Britain thereafter. Given the potential difficulty for terrestrial species to colonize Ireland except by human introduction, we investigated the stoat (Mustela erminea) as a possible cold-tolerant model species for natural colonization of Ireland at the LGM itself. The stoat currently lives in Ireland and Britain and across much of the Holarctic region including the high Arctic. We studied mitochondrial DNA variation (1771 bp) over the whole geographical range of the stoat (186 individuals and 142 localities), but with particular emphasis on the British Isles and continental Europe. Irish stoats showed considerably greater nucleotide and haplotype diversity than those in Britain. Bayesian dating is consistent with an LGM colonization of Ireland and suggests that Britain was colonized later. This later colonization probably reflects a replacement event, which can explain why Irish and British stoats belong to different mitochondrial lineages as well as different morphologically defined subspecies. The molecular data strongly indicate that stoats colonized Ireland naturally and that their genetic variability reflects accumulation of mutations during a population expansion on the island.

High incidence of nonslippage mechanisms generating variability and complexity in eurasian badger microsatellites

The use of microsatellites in population genetics is hindered by a lack of understanding of the pattern and origin of mutations, the need to develop more specific and better computational models, and a paucity of information about specific taxa and loci. We analyzed between 4 and 10 allele sequences from 10 different microsatellites in Eurasian badgers in order to determine the compliance of the sequences with stepwise mutation models and the origin of that variability which cannot be detected through standard genotyping procedures. All microsatellite loci exhibited imperfections and/or substitutions and indels in the flanking region, as well as additions or deletions of repeat units. Our data set of sequences showed a higher number of imperfect repeats than other published badger and carnivore sequences. This could be attributed to the process of loci isolation because when genetic variability is low, researchers may be more likely to use imperfect loci if these are variable in the population being studied. Locus Mel15 had 2 repetitive arrays: one was part of a polypyrimidine region of a carnivoran short interspersed nuclear element (CAN-SINE) and the other was located in an A-rich region typical of these insertions. In spite of this complexity, heterozygosity was correlated with the maximum number of repeats. Thus, although new theoretical models are being evolved to cover complex patterns of microsatellite mutation, sequencing electromorphs is needed to identify microsatellites or portions of them whose evolution can be modeled under simple models.

Molecular phylogenetic study on the origin and evolution of Mustelidae

The family Mustelidae, which consists of Mustelinae, Lutrinae, Melinae, and Taxidiinae, is the largest family among Carnivora and is a highly diverse group. Recent molecular phylogenetic studies have clarified the phylogenetic relations among Mustelidae, but there remain several unresolved problems, particularly concerning the deep branchings. Whereas many studies support the monophyly of Mustelidae+Procyonidae among Musteloidea, the relations between Mustelidae+Procyonidae, Ailuridae, and Miphitidae are still unclear. To address these problems, we inferred a tree on the basis of the sequences of mitochondrial genomes and of multiple nuclear genes using the maximum likelihood method. Our results strongly support the hypothesis that the Taxidiinae branched at first, followed by the branching of the Melinae. After that, Mustelinae diversified, and Lutrinae evolved within Mustelinae. With respect to the deep branchings in Musteloidea, the Ailuridae/Mephitidae monophyly tree and the Mephitidae-basal tree are indistinguishable in log-likelihood score, and this problem remains unresolved.

[Genetic structure of the sable Martes zibellina L. populations from magadan oblast as inferred from mitochondrial DNA variation]

Restriction polymorphism of the mtDNA cytochrome b gene was studied in nine sable Martes zibellina L. populations from three introduction foci of Khabarovsk and Kamchatka sables in Magadan oblast: Olya, Kolyma, and Omolon. For comparison, similar studies were performed with the populations of central Kamchatka and Khabarovsk krai. In total, 444 DNA specimens were examined. Three mtDNA haplotypes (A, B, and C) proved to occur at various frequencies in the populations under study. The sable population system displayed high differentiation (FST = 22.3%). The populations of the Olya focus were most similar genetically to the populations of Kamchatka; those of the Omolon focus were similar to the Khabarovsk populations, and those of the Kolyma focus occupied an intermediate place. The observed spatial heterogeneity of the sable populations of Magadan oblast was explained in terms of the formation of the introduction foci of Kamchatka and Khabarovsk sables, starting from the 1950s.

Validation of the barcoding gene COI for use in forensic genetic species identification

The application of forensics to wildlife crime investigation routinely involves genetic species identification based on DNA sequence similarity. This work can be hindered by a lack of authenticated reference DNA sequence data resulting in weak matches between evidence and reference samples. The introduction of DNA barcoding has highlighted the expanding use of the mtDNA gene, cytochrome c oxidase I (COI), as a genetic marker for species identification. Here, we assess the COI gene for use in forensic analysis following published human validation guidelines. Validation experiments investigated reproducibility, heteroplasmy, mixed DNA, DNA template concentration, chemical treatments, substrate variation, environmental conditions and thermocycling parameters. Sequence similarity searches using both GenBank BLASTn and BOLD search engines indicated that the COI gene consistently identifies species where authenticated reference sequence data exists. Where misidentification occurred the cause was attributable to either erroneous reference sequences from published data, or lack of primer specificity. Although amplification failure was observed under certain sample treatments, there was no evidence of environmentally induced sequence mutation in those sequences that were generated. A simulated case study compared the performance of COI and cytochrome b mtDNA genes. Findings are discussed in relation to the utility of the COI gene in forensic species identification.

Evidence from nuclear DNA sequences sheds light on the phylogenetic relationships of Pinnipedia: single origin with affinity to Musteloidea

Considerable long-standing controversy and confusion surround the phylogenetic affinities of pinnipeds, the largely marine group of "fin-footed" members of the placental mammalian order Carnivora. Until most recently, the two major competing hypotheses were that the pinnipeds have a single (monophyletic) origin from a bear-like ancestor, or that they have a dual (diphyletic) origin, with sea lions (Otariidae) derived from a bear-like ancestor, and seals (Phocidae) derived from an otter-, mustelid-, or musteloid-like ancestor. We examined phylogenetic relationships among 29 species of arctoid carnivorans using a concatenated sequence of 3228 bp from three nuclear loci (apolipoprotein B, APOB; interphotoreceptor retinoid-binding protein, IRBP; recombination-activating gene 1, RAG1). The species represented Pinnipedia (Otariidae: Callorhinus, Eumetopias; Phocidae: Phoca), bears (Ursidae: Ursus, Melursus), and Musteloidea (Mustelidae: Mustela, Enhydra, Melogale, Martes, Gulo, Meles; Procyonidae: Procyon; Ailuridae: Ailurus; Mephitidae: Mephitis). Maximum parsimony, maximum likelihood, and Bayesian inference phylogenetic analyses of separate and combined datasets produced trees with largely congruent topologies. The analyses of the combined dataset resulted in well-resolved and well-supported phylogeny reconstructions. Evidence from nuclear DNA evolution presented here contradicts the two major hypotheses of pinniped relationships and strongly suggests a single origin of the pinnipeds from an arctoid ancestor shared with Musteloidea to the exclusion of Ursidae.

The Unusual Adaptive Expansion of Pancreatic Ribonuclease Gene in Carnivora

Pancreatic ribonuclease (RNASE1) is a digestive enzyme that has been recognized to be one of the most attractive model systems for molecular evolutionary studies. The contribution of RNASE1 gene duplication to the functional adaptation of digestive physiology in foregut-fermenting herbivores, mostly in ruminants, has been well documented. However, no one has ever done a comprehensive study on the carnivores, which are sister to the artiodactyls. Here, we sequenced this gene from 15 species of the superfamily Caniformia in order Carnivora, which all have a relatively simple digestive system and lack the microbial digestion in rumen or cecum typical of most herbivores. In contrast to our initial expectation that only a single RNASE1 gene is present in these carnivores, we observed a "birth (gene duplication)-and-death (gene deactivation)" process for the evolution of RNASE1 genes in all 3 species of Mustelidae family examined here, adding the growing diversity of RNASE1 gene family evolution. In addition, bursts of positive selection have been shown to contribute the enigmatic diversification of these RNASE1 genes in Mustelidae. The finding of the adaptive expansion of RNASE1 in animals without foregut fermentation provides another opportunity for further studies of the structure, function, and evolution of this gene, raising the possibility that new tissue specificity or other functions of RNASE1 genes might have developed in these species.

Comparative phylogeography between the ermine Mustela erminea and the least weasel M. nivalis of Palaearctic and Nearctic regions, based on analysis of mitochondrial DNA control region sequences

Phylogeography of the ermine Mustela erminea and the least weasel M. nivalis from Palaearctic and Nearctic regions were investigated based on mitochondrial DNA control region sequences. Mustela erminea exhibited a very low level of genetic variation, and geographic structures among populations were unclear. This may indicate that M. erminea recently reoccupied a wide territory in Eurasia following the last glacial retreat. In comparison with M. erminea, genetic variations within and among populations of M. nivalis were much greater. Molecular phylogenetic relationships showed that two lineages of M. nivalis occurred in the Holarctic region: one spread from the Eurasian region to North America, and the other occurred in south-eastern Europe, the Caucasus and Central Asia. The results suggest either mitochondrial DNA introgression among populations of south-eastern Europe, the Caucasus and Central Asia, or ancestral polymorphisms remaining in those populations. Contrastive phylogeographic patterns between the two mustelid species could reflect differences of their migration histories in Eurasia after the last glacial age.

Dispersal and genetic structure in the American marten, Martes americana

Natal dispersal in a vagile carnivore, the American marten (Martes americana), was studied by comparing radio-tracking data and microsatellite genetic structure in two populations occupying contrasting habitats. The genetic differentiation determined among groups of individuals using F(ST) indices appeared to be weak in both landscapes, and showed no increase with geographical distance. Genetic structure investigated using pairwise genetic distances between individuals conversely showed a pattern of isolation by distance (IBD), but only in the population occurring in a homogeneous high-quality habitat, therefore showing the advantage of individual-based analyses in detecting within-population processes and local landscape effects. The telemetry study of juveniles revealed a leptokurtic distribution of dispersal distances in both populations, and estimates of the mean squared parent-offspring axial distance (sigma2) inferred both from the genetic pattern of IBD and from the radio-tracking survey showed that most juveniles make little contribution to gene flow.