New data on the phylogeography and genetic diversity of the brown bear Ursus arctos Linnaeus, 1758 of Northeastern Eurasia (mtDNA control region polymorphism analysis)

An analysis of polymorphism of the fragment of the control region of mitochondrial DNA of 53 tissue samples of the brown bear Ursus arctos from several regions of the eastern part of Russia was carried out. It was found that most of the described haplotypes belong to cluster 3a, the most common in Eurasia, and do not form regionally specific haplogroups. However, among the bears from Western and Eastern Siberia, as well as the island of Kunashir, three haplotypes were identified, which are close to the haplogroup typical of Eastern Hokkaido bears. The assumption was made of the existence in Siberia and the Far East of one or more Pleistocene refugia.     

Admixture and Gene Flow from Russia in the Recovering Northern European Brown Bear (Ursus arctos)

Large carnivores were persecuted to near extinction during the last centuries, but have now recovered in some countries. It has been proposed earlier that the recovery of the Northern European brown bear is supported by migration from Russia. We tested this hypothesis by obtaining for the first time continuous sampling of the whole Finnish bear population, which is located centrally between the Russian and Scandinavian bear populations. The Finnish population is assumed to experience high gene flow from Russian Karelia. If so, no or a low degree of genetic differentiation between Finnish and Russian bears could be expected. We have genotyped bears extensively from all over Finland using 12 validated microsatellite markers and compared their genetic composition to bears from Russian Karelia, Sweden, and Norway. Our fine masked investigation identified two overlapping genetic clusters structured by isolation-by-distance in Finland (pairwise F_ST = 0.025). One cluster included Russian bears, and migration analyses showed a high number of migrants from Russia into Finland, providing evidence of eastern gene flow as an important driver during recovery. In comparison, both clusters excluded bears from Sweden and Norway, and we found no migrants from Finland in either country, indicating that eastern gene flow was probably not important for the population recovery in Scandinavia. Our analyses on different spatial scales suggest a continuous bear population in Finland and Russian Karelia, separated from Scandinavia.     

Geographic and genetic boundaries of brown bear (Ursus arctos) population in the Caucasus

The taxonomic status of brown bears in the Caucasus remains unclear. Several morphs or subspecies have been identified from the morphological (craniological) data, but the status of each of these subspecies has never been verified by molecular genetic methods. We analysed mitochondrial DNA sequences (control region) to reveal phylogenetic relationships and infer divergence time between brown bear subpopulations in the Caucasus. We estimated migration and gene flow from both mitochondrial DNA and microsatellite allele frequencies, and identified possible barriers to gene flow among the subpopulations. Our suggestion is that all Caucasian bears belong to the nominal subspecies of Ursus arctos. Our results revealed two genetically and geographically distinct maternal haplogroups: one from the Lesser Caucasus and the other one from the Greater Caucasus. The genetic divergence between these haplogroups dates as far back as the beginning of human colonization of the Caucasus. Our analysis of the least‐cost distances between the subpopulations suggests humans as a major barrier to gene flow. The low genetic differentiation inferred from microsatellite allele frequencies indicates that gene flow between the two populations in the Caucasus is maintained through the movements of male brown bears. The Likhi Ridge that connects the Greater and Lesser Caucasus mountains is the most likely corridor for this migration.     

Connectivity and population subdivision at the fringe of a large brown bear (Ursus arctos) population in North Western Europe

Loss of connectivity and habitat destruction may lead to genetic depletion of wild animal populations, especially in species requiring large, connected territories as the brown bear (Ursus arctos). Brown bear populations of North Western Russia, Finland and Northern Norway have been assumed to form one large, continuous population; however this hypothesis has not been tested sufficiently. We have genotyped 1,887 samples from 2005 to 2008 from four distinct areas and used the resulting DNA profiles from 146 different individuals to analyze the genetic diversity, population structure, and the migration rates among groups. In addition, we have tested for traces of previous genetic bottlenecks. Individuals from Eastern Finland and Russian Karelia were grouped in the same cluster (“Karelia”), while distinctive subpopulations of brown bears were detected in the north (“Pasvik”), and the east (“Pinega”). All three subpopulations displayed high genetic variation, with expected heterozygosities (H _E) of 0.77–0.81, but differentiation among the clusters was relatively low (average F _ST?=?0.051, P?<?0.001). No evidence of genetic bottlenecks in the past was found. We detected a highly significant isolation-by-distance (IBD) pattern. For Pasvik, self-recruitment was found to be very high (96%), pointing to the possibility of genetic isolation. In contrast, between Karelia and Pinega we detected high, bi-directional migration rates (~30%), indicating genetic exchange. Conclusively, despite of a substantial influence of IBD on the genetic structure in the region, we detected considerable variation in connectivity among the identified clusters that could not be explained solely by the distance between them.     

Phylogeographic and Demographic Analysis of the Asian Black Bear (Ursus thibetanus) Based on Mitochondrial DNA

The Asian black bear Ursus thibetanus is widely distributed in Asia and is adapted to broad-leaved deciduous forests, playing an important ecological role in the natural environment. Several subspecies of U. thibetanus have been recognized, one of which, the Japanese black bear, is distributed in the Japanese archipelago. Recent molecular phylogeographic studies clarified that this subspecies is genetically distantly related to continental subspecies, suggesting an earlier origin. However, the evolutionary relationship between the Japanese and continental subspecies remained unclear. To understand the evolution of the Asian black bear in relation to geological events such as climatic and transgression-regression cycles, a reliable time estimation is also essential. To address these issues, we determined and analyzed the mt-genome of the Japanese subspecies. This indicates that the Japanese subspecies initially diverged from other Asian black bears in around 1.46Ma. The Northern continental population (northeast China, Russia, Korean peninsula) subsequently evolved, relatively recently, from the Southern continental population (southern China and Southeast Asia). While the Japanese black bear has an early origin, the tMRCAs and the dynamics of population sizes suggest that it dispersed relatively recently in the main Japanese islands: during the late Middle and Late Pleistocene, probably during or soon after the extinction of the brown bear in Honshu in the same period. Our estimation that the population size of the Japanese subspecies increased rapidly during the Late Pleistocene is the first evidential signal of a niche exchange between brown bears and black bears in the Japanese main islands.This interpretation seems plausible but was not corroborated by paleontological evidence that fossil record of the Japanese subspecies limited after the Late Pleistocene. We also report here a new fossil record of the oldest Japanese black bear from the Middle Pleistocene, and it supports our new evolutionary hypothesis of the Japanese black bear.     

Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution

Despite extensive genetic analysis, the evolutionary relationship between polar bears (Ursus maritimus) and brown bears (U. arctos) remains unclear. The two most recent comprehensive reports indicate a recent divergence with little subsequent admixture or a much more ancient divergence followed by extensive admixture. At the center of this controversy are the Alaskan ABC Islands brown bears that show evidence of shared ancestry with polar bears. We present an analysis of genome-wide sequence data for seven polar bears, one ABC Islands brown bear, one mainland Alaskan brown bear, and a black bear (U. americanus), plus recently published datasets from other bears. Surprisingly, we find clear evidence for gene flow from polar bears into ABC Islands brown bears but no evidence of gene flow from brown bears into polar bears. Importantly, while polar bears contributed <1% of the autosomal genome of the ABC Islands brown bear, they contributed 6.5% of the X chromosome. The magnitude of sex-biased polar bear ancestry and the clear direction of gene flow suggest a model wherein the enigmatic ABC Island brown bears are the descendants of a polar bear population that was gradually converted into brown bears via male-dominated brown bear admixture. We present a model that reconciles heretofore conflicting genetic observations. We posit that the enigmatic ABC Islands brown bears derive from a population of polar bears likely stranded by the receding ice at the end of the last glacial period. Since then, male brown bear migration onto the island has gradually converted these bears into an admixed population whose phenotype and genotype are principally brown bear, except at mtDNA and X-linked loci. This process of genome erosion and conversion may be a common outcome when climate change or other forces cause a population to become isolated and then overrun by species with which it can hybridize.     

Fourth report of the cooperative, open-ended study of slowly growing mycobacteria by the International Working Group on Mycobacterial Taxonomy.

The open-ended study of the International Working Group on Mycobacterial Taxonomy is an ongoing project to characterize slowly growing strains of mycobacteria that do not belong to well-established or thoroughly characterized species. In this fourth report we describe two numerical taxonomic clusters that represent subspecies or biovars of Mycobacterium simiae, one cluster that encompasses the erstwhile type strain of the presently invalid species "Mycobacterium paraffinicum," one cluster that is phenotypically very similar to Mycobacterium avium and Mycobacterium intracellulare but may be a separate genospecies, one cluster that appears to be phenotypically distinct from M. avium but reacts with a nucleic acid probe specific for M. avium, and three tentatively defined clusters in proximity to a cluster that encompasses the type strain of Mycobacterium malmoense. Of special practical interest is the fact that one of the latter three clusters is composed of clinically significant scotochromogenic bacteria that can be misidentified as the nonpathogenic organism Mycobacterium gordonae if insufficient biochemical tests are performed.     

Population genetic isolation and limited connectivity in the purple finch (Haemorhous purpureus)

Using a combination of mitochondrial and z‐linked sequences, microsatellite data, and spatio‐geographic modeling, we examined historical and contemporary factors influencing the population genetic structure of the purple finch (Haemorhous purpureus). Mitochondrial DNA data show the presence of two distinct groups corresponding to the two subspecies, H. p. purpureus and H. p. californicus. The two subspecies likely survived in separate refugia during the last glacial maximum, one on the Pacific Coast and one east of the Rocky Mountains, and now remain distinct lineages with little evidence of gene flow between them. Southwestern British Columbia is a notable exception, as subspecies mixing between central British Columbia and Vancouver Island populations suggests a possible contact zone in this region. Z‐linked data support two mitochondrial groups; however, Coastal Oregon and central British Columbia sites show evidence of mixing. Contemporary population structure based on microsatellite data identified at least six genetic clusters: three H. p. purpureus clusters, two H. p. californicus clusters, and one mixed cluster, which likely resulted from high site fidelity and isolation by distance, combined with sexual selection on morphological characters reinforcing subspecies differences.     

Implications of the Circumpolar Genetic Structure of Polar Bears for Their Conservation in a Rapidly Warming Arctic

We provide an expansive analysis of polar bear (Ursus maritimus) circumpolar genetic variation during the last two decades of decline in their sea-ice habitat. We sought to evaluate whether their genetic diversity and structure have changed over this period of habitat decline, how their current genetic patterns compare with past patterns, and how genetic demography changed with ancient fluctuations in climate. Characterizing their circumpolar genetic structure using microsatellite data, we defined four clusters that largely correspond to current ecological and oceanographic factors: Eastern Polar Basin, Western Polar Basin, Canadian Archipelago and Southern Canada. We document evidence for recent (ca. last 1–3 generations) directional gene flow from Southern Canada and the Eastern Polar Basin towards the Canadian Archipelago, an area hypothesized to be a future refugium for polar bears as climate-induced habitat decline continues. Our data provide empirical evidence in support of this hypothesis. The direction of current gene flow differs from earlier patterns of gene flow in the Holocene. From analyses of mitochondrial DNA, the Canadian Archipelago cluster and the Barents Sea subpopulation within the Eastern Polar Basin cluster did not show signals of population expansion, suggesting these areas may have served also as past interglacial refugia. Mismatch analyses of mitochondrial DNA data from polar and the paraphyletic brown bear (U. arctos) uncovered offset signals in timing of population expansion between the two species, that are attributed to differential demographic responses to past climate cycling. Mitogenomic structure of polar bears was shallow and developed recently, in contrast to the multiple clades of brown bears. We found no genetic signatures of recent hybridization between the species in our large, circumpolar sample, suggesting that recently observed hybrids represent localized events. Documenting changes in subpopulation connectivity will allow polar nations to proactively adjust conservation actions to continuing decline in sea-ice habitat.     

Molecular genetic diversity of musk deer Moschus moschiferus L., 1758 (Ruminantia, Artiodactyla) from the northern subspecies group

Genetic diversity within the northern subspecies group of musk deer Moschus moschiferus L., 1758 was examined based on the mtDNA control region hypervariable fragment (300-bp) sequence polymorphism. Nucleotide diversity, constituting 2.6% for the whole sample (n = 34), varied in the range from 0.6 to 1.9% for individual subspecies. Maximum values of this index were observed for Siberian subspecies (M. m. moschiferus), which had the widest range. Genetic similarity between the haplotypes of the musk deer from the Far East (Russia) and Sakhalin Island, which grouped in one cluster in a phylogenetic tree, was demonstrated. The data obtained indicate that the distribution of musk deer along the territory of Russia occurred from Eastern Siberia to the Far East, and from there to the Sakhalin Island. A currently observed decrease of the musk deer population number along with the increased habitat fragmentation can result in a decrease of the total genetic diversity and in inbreeding depression in the local isolated groups.     

Genetic structure of a wide-spectrum chicken gene pool

The genetic structure of 65 chicken populations was studied using 29 simple sequence repeat loci. Six main clusters which corresponded to geographical origins and histories were identified: Brown Egg Layers; predominantly Broilers; native Chinese breeds or breeds with recent Asian origin; predominantly breeds of European derivation; a small cluster containing populations with no common history and populations that had breeding history with White Leghorn. Another group of populations that shared their genome with several clusters was defined as 'Multi-clusters'. Gallus gallus gallus (Multi-clusters), one of the subspecies of the Red Jungle Fowl, which was previously suggested to be one of the ancestors of the domesticated chicken, has almost no shared loci with European and White Egg layer populations. In a further sub-clustering of the populations, discrimination between all the 65 populations was possible, and relationships between each were suggested. The genetic variation between populations was found to account for about 34% of the total genetic variation, 11% of the variation being between clusters and 23% being between populations within clusters. The suggested clusters may assist in future studies of genetic aspects of the chicken gene pool.     

Mitochondrial cytochrome b gene variation in brown bear (Ursus arctos Linnaeus, 1758) from southern part of Russian Far East

The genetic variability of brown bear Ursus arctos from the southern part of the Russian Far East was first examined based on the variations in the mitochondrial DNA cytochrome b sequence. The presence of two phylogenetic groups of haplotypes described previously for other parts of the species range was demonstrated. Part of the samples belonged to the haplotype group distributed across the whole range, while another part belonged to the rare group previously only reported for Japan and Alaska. These findings partially clarify the pattern of brown-bear colonization on the territory of the Russian Far East and Japan.     

Genetic diversity of endangered brown bear (Ursus arctos) populations at the crossroads of Europe, Asia and Africa

Aim  Middle East brown bears ( Ursus arctos syriacus Hemprich and Ehrenberg, 1828) are presently on the edge of extinction. However, little is known of their genetic diversity. This study investigates that question as well as that of Middle East brown bear relationships to surrounding populations of the species.
Location  Middle East region of south-western Asia.
Methods  We performed DNA analyses on 27 brown bear individuals. Twenty ancient bone samples (Late Pleistocene to 20th century) from natural populations and seven present-day samples obtained from captive individuals were analysed.
Results  Phylogenetic analyses of the mitochondrial sequences obtained from seven ancient specimens identify three distinct maternal clades, all unrelated to one recently described from North Africa. Brown bears from Iran exhibit striking diversity (three individuals, three haplotypes) and form a unique clade that cannot be linked to any extant one. Individuals from Syria belong to the Holarctic clade now observed in Eastern Europe, Turkey, Japan and North America. Specimens from Lebanon surprisingly appear as tightly linked to the clade of brown bears now in Western Europe. Moreover, we show that U. a. syriacus in captivity still harbour haplotypes closely linked to those found in ancient individuals.
Main conclusion  This study brings important new information on the genetic diversity of brown bear populations at the crossroads of Europe, Asia and Africa. It reveals a high level of diversity in Middle East brown bears and extends the historical distribution of the Western European clade to the East. Our analyses also suggest the value of a specific breeding programme for captive populations.     

Assumed and inferred spatial structure of populations: the Scandinavian brown bears revisited

We reanalysed the spatial structure of the Scandinavian brown bear (Ursus arctos) population based on multilocus genotypes. We used data from a former study that had presumed a priori a specific population subdivision based on four subpopulations. Using two independent methods (neighbour-joining trees and Bayesian assignment tests), we analysed the data without any prior presumption about the spatial structure. A subdivision of the population into three subpopulations emerged from our study. The genetic pattern of these subpopulations matched the three geographical clusters of individuals present in the population. We recommend considering the Scandinavian brown bear population as consisting of three (instead of four) subpopulations. Our results underline the importance of determining genetic structure from the data, without presupposing a structure, even when there seems to be good reason to do so.     

青藏高原可可西里地区藏棕熊暖季食性及采食行为模式

藏棕熊(Ursus arctos pruinosus)是青藏高原特有的棕熊亚种,作者曾对该地区藏棕熊夏季食性进行了初步报道(Xu et al,2006),然而,藏棕熊的采食行为模式一直未见报道。2009年7-8月,作者又对可可西里地区藏棕熊食性及采食行为模式做了补充调查研究,对两次考察所获得的数据进行了整合分析,研究结果表明,该地区藏棕熊主要以动物性食物为主,其中,高原鼠兔(Ochotona curzoniae)的相对频次为37.3%和干物质量为44.7%,下同);野牦牛(Bos grunniens)分别为18.7%和30.2%;藏羚(Pantholops hodgsoni)分别为15.0%和16.2%。藏棕熊在可可西里地区有两种采食行为模式:主动捕食高原鼠兔和采食藏羚、藏原羚和野牦牛尸体。观察期间藏棕熊约用10%的时间挖掘高原鼠兔的洞穴捕捉高原鼠兔,但未见藏棕熊主动捕食大型哺乳动物。粪样分析结果发现,藏棕熊主动捕食的高原鼠兔和喜马拉雅旱獭(Marmota himalayana)和通过食腐方式获得的藏羚、藏原羚和野牦牛的生物量基本相等。     

Mandible size and shape in extant Ursidae (Carnivora,Mammalia): A tool for taxonomy and ecogeography

The family Ursidae is currently one of the taxonomic groups with the lowest number of species among Carnivora. Extant bear species exhibit broad ecological adaptations both at inter‐ and intraspecific level, and taxonomic issues within this family remain unresolved (i.e., the number of recognizable subspecies). Here, we investigate a sample of bear mandibles using two‐dimensional geometric morphometrics to better characterize bear taxonomy and evolution with a focus on one of the most widespread species: the brown bear (Ursus arctos). Our analyses confirm that both size and shape data are useful continuous characters that discriminate with very high percentage of accuracy extant bears. We also identify two very distinct mandibular morphologies in the subspecies Ursus actos isabellinus and Ursus arctos marsicanus. These taxa exhibit a high degree of morphological differentiation possibly as a result of a long process of isolation. Ecogeographical variation occurs among bear mandibles with climate impacting the diversification of the whole family.     

Underestimated mitochondrial diversity in gypsy moth Lymantria dispar from Asia

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Noninvasive genetic assessment of brown bear population structure in Bulgarian mountain regions

The Balkans are one of the last large refugia for brown bear (Ursus arctos) populations in Europe, and Bulgaria, in particular, contains relatively large areas of suitable brown bear habitat and a potential population of more than 600 individuals. Despite this, the majority of brown bear research remains focused on bear populations in Central and Western Europe. We provide the first assessment of genetic population structure of brown bears in Bulgaria by analysing tissue samples (n = 16) as well as samples collected with noninvasive genetic methods, including hair and faecal samples (n = 189 and n = 163, respectively). Sequence analysis of a 248 base pair fragment of the mitochondrial control region showed that two highly divergent mitochondrial European brown bear lineages form a contact zone in central Bulgaria. Furthermore, the analysis of 13 polymorphic microsatellite markers identified 136 individuals and found substantial genetic variability (H_e = 0.74; N_A = 8.9). The combination of both genetic markers revealed the presence of weak genetic substructure in the study area with considerable degrees of genetic admixture and the likely presence of migration corridors between the two subpopulation in the Rhodope Mountains and Stara Planina as evidenced from the genetic detection of two male long-distance dispersers. A detailed assessment from densely collected samples in the Rhodope Mountains resulted in a population size estimate of 315 (95% CI = 206–334) individuals, indicating that not all available habitat is presently occupied by bears in this region. Efficient management plans should focus on preserving connectivity of suitable habitats in order to maintain gene flow between the two Bulgarian brown bear subpopulations.     

Molecular genetic diversity of musk deer Moschus moschiferus L., 1758 (Ruminantia, Artiodactyla) from the northern subspecies group

Genetic diversity within the northern subspecies group of musk deer Moschus moschiferus L, 1758 was examined based on the mtDNA control region hypervariable fragment (300-bp) sequence polymorphism. Nucleotide diversity, constituting 2.6% for the whole sample (n = 34), varied in the range from 0.6 to 1.9% for individual subspecies. Maximum values of this index were observed for Siberian subspecies (M. m. moschiferus), which had the widest range. Genetic similarity between the haplotypes of the musk deer from the Far East (Russia) and Sakhalin Island, which grouped in one cluster in a phylogenetic tree, was demonstrated. The data obtained indicate that the distribution of musk deer along the territory of Russia occurred from Eastern Siberia to the Far East, and from there to the Sakhalin Island. A currently observed decrease of the musk deer population number along with the increased habitat fragmentation can result in a decrease of the total genetic diversity and in inbreeding depression in the local isolated groups.