596 research outputs found
Most Northerly Observation of a Grizzly Bear (Ursus arctos) in Canada: Photographic and DNA Evidence from Melville Island, Northwest Territories
During geological studies in 2003 and 2004 on Melville Island, Northwest Territories, Canada, field parties photographed and gathered genetic information on one or more grizzly bears (Ursus arctos). To our knowledge, these data constitute the most northerly observations made of this species in North America. The DNA of a hair sample collected on Melville Island in 2004 is genetically indistinguishable from DNA collected from a population of grizzly bears around Paulatuk, Northwest Territories, along the northern mainland coast. It is also distinct from the DNA of the Viscount Melville polar bear (Ursus maritimus) population. Our evidence and review suggest that, at a minimum, transient grizzly bears are now regular visitors to the Canadian Arctic Archipelago. More research will be required to understand the significance of these observations, but a small viable population of grizzly bears may now be using areas in or around Melville Island.Dans le cadre dâĂ©tudes gĂ©ologiques rĂ©alisĂ©es en 2003 et en 2004 sur lâĂźle Melville, dans les Territoires du Nord-Ouest, au Canada, des chercheurs sur le terrain ont photographiĂ© et recueilli de lâinformation gĂ©nĂ©tique sur un ou plusieurs grizzlys (Ursus arctos). Ă notre connaissance, il sâagit des donnĂ©es reprĂ©sentant les observations sur cette espĂšce qui ont Ă©tĂ© recueillies les plus au nord de lâAmĂ©rique du Nord. LâADN dâun Ă©chantillon de poil prĂ©levĂ© sur lâĂźle Melville en 2004 est indiffĂ©renciable, du point de vue gĂ©nĂ©tique, de lâADN prĂ©levĂ© au sein dâune population de grizzlys de la rĂ©gion de Paulatuk, Territoires du Nord-Ouest, le long de la cĂŽte nord. Par ailleurs, il est distinct de lâADN de la population dâours polaires du Vicomte de Melville (Ursus maritimus). DâaprĂšs les preuves que nous avons recueillies et notre analyse, Ă tout le moins, les grizzlys de passage sont maintenant des visiteurs habituels dans lâarchipel Arctique canadien. Dâautres recherches devront ĂȘtre effectuĂ©es afin de comprendre lâimportance de ces observations, mais une population petite, bien que viable, de grizzlys pourrait maintenant utiliser les rĂ©gions de lâĂźle Melville ou situĂ©es tout prĂšs
The memory space: Exploring future uses of Web 2.0 and mobile internet through design interventions.
The QuVis Quantum Mechanics Visualization project aims to address challenges
of quantum mechanics instruction through the development of interactive
simulations for the learning and teaching of quantum mechanics. In this
article, we describe evaluation of simulations focusing on two-level systems
developed as part of the Institute of Physics Quantum Physics resources.
Simulations are research-based and have been iteratively refined using student
feedback in individual observation sessions and in-class trials. We give
evidence that these simulations are helping students learn quantum mechanics
concepts at both the introductory and advanced undergraduate level, and that
students perceive simulations to be beneficial to their learning.Comment: 15 pages, 5 figures, 1 table; accepted for publication in the
American Journal of Physic
Identification of the barrier to gene flow between phylogeographic lineages of the common hamster Cricetus cricetus
In anthropogenically disturbed habitats, natural barriers still exist and have to be recognized, as they are important for conservation measures. Areas of phylogeographic breaks within a species are often stabilized in inhospitable regions which act as natural barriers. An area of contact between phylogeographic lineages of the common hamster (Cricetus cricetus) was found in the MaĆopolska Upland in Poland. A total of 142 common hamsters were captured between 2005 and 2009. All hamsters were genotyped at 17 microsatellite loci and partial sequences of the mitochondrial (mtDNA) control region were obtained. No mixed populations with mtDNA haplotypes of both lineages were found. The distance between marginal populations was about 20Â km; no hamsters were found in the area between. A principal components analysis (PCA) was performed on microsatellite data and the greatest change in PC1 scores was found between marginal samples. To define the habitat components responsible for the phylogeographic break, we compared the habitat composition of sites occupied by hamsters with those from which hamsters were absent. We found that hamsters avoided forested areas and sandy soils. The area of the potential barrier was characterized by a high proportion of woodland and unfavorable soils in comparison with neighboring areas inhabited by hamsters. They cannot settle in this area due to their high winter mortality in shallow burrows and high predation in the fields adjacent to forests
Massive Nest-Box Supplementation Boosts Fecundity, Survival and Even Immigration without Altering Mating and Reproductive Behaviour in a Rapidly Recovered Bird Population
Habitat restoration measures may result in artificially high breeding density, for instance when nest-boxes saturate the environment, which can negatively impact species' demography. Potential risks include changes in mating and reproductive behaviour such as increased extra-pair paternity, conspecific brood parasitism, and polygyny. Under particular cicumstances, these mechanisms may disrupt reproduction, with populations dragged into an extinction vortex. With the use of nuclear microsatellite markers, we investigated the occurrence of these potentially negative effects in a recovered population of a rare secondary cavity-nesting farmland bird of Central Europe, the hoopoe (Upupa epops). High intensity farming in the study area has resulted in a total eradication of cavity trees, depriving hoopoes from breeding sites. An intensive nest-box campaign rectified this problem, resulting in a spectacular population recovery within a few years only. There was some concern, however, that the new, high artificially-induced breeding density might alter hoopoe mating and reproductive behaviour. As the species underwent a serious demographic bottleneck in the 1970â1990s, we also used the microsatellite markers to reconstitute the demo-genetic history of the population, looking in particular for signs of genetic erosion. We found i) a low occurrence of extra-pair paternity, polygyny and conspecific brood parasitism, ii) a high level of neutral genetic diversity (mean number of alleles and expected heterozygosity per locus: 13.8 and 83%, respectively) and, iii) evidence for genetic connectivity through recent immigration of individuals from well differentiated populations. The recent increase in breeding density did thus not induce so far any noticeable detrimental changes in mating and reproductive behaviour. The demographic bottleneck undergone by the population in the 1970s-1990s was furthermore not accompanied by any significant drop in neutral genetic diversity. Finally, genetic data converged with a concomitant demographic study to evidence that immigration strongly contributed to local population recovery
Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus
Coastal lagoons are semi-isolated ecosystems
exposed to wide fluctuations of environmental conditions
and showing habitat fragmentation. These features may
play an important role in separating species into different
populations, even at small spatial scales. In this study, we
evaluate the concordance between mitochondrial (previous
published data) and nuclear data analyzing the genetic
variability of Pomatoschistus marmoratus in five localities,
inside and outside the Mar Menor coastal lagoon (SE
Spain) using eight microsatellites. High genetic diversity
and similar levels of allele richness were observed across
all loci and localities, although significant genic and
genotypic differentiation was found between populations
inside and outside the lagoon. In contrast to the FST values
obtained from previous mitochondrial DNA analyses
(control region), the microsatellite data exhibited significant
differentiation among samples inside the Mar Menor
and between lagoonal and marine samples. This pattern
was corroborated using Cavalli-Sforza genetic distances.
The habitat fragmentation inside the coastal lagoon and
among lagoon and marine localities could be acting as a
barrier to gene flow and contributing to the observed
genetic structure. Our results from generalized additive
models point a significant link between extreme lagoonal
environmental conditions (mainly maximum salinity) and
P. marmoratus genetic composition. Thereby, these environmental
features could be also acting on genetic structure
of coastal lagoon populations of P. marmoratus favoring
their genetic divergence. The mating strategy of P. marmoratus
could be also influencing our results obtained from
mitochondrial and nuclear DNA. Therefore, a special
consideration must be done in the selection of the DNA
markers depending on the reproductive strategy of the
species
Characterization of six microsatellite loci in Myrica faya (Myricaceae) and cross amplification in the endangered endemic M. rivas-martinezii in Canary Islands, Spain
Six novel polymorphic microsatellite markers were isolated from enriched libraries in Myrica faya Ait., recently renamed Morella faya, (fayatree, firetree, or firebush) in order to examine the genetic diversity in natural populations. Also, test cross-specific amplification and genetic diversity in Myrica rivas-martinezii, which is endemic on the Canary islands. Microsatellite loci were screened in 225 individuals of both species from different islands of the Canarian archipelago. All markers were successfully amplified from both Myrica species, with an average number of 6.5 and 9.3 alleles per locus in M. rivas-martinezii and M. faya, respectively. There was no evidence for linkage disequilibrium between loci, and the probability of null alleles ranged from 0.01 to 0.17
Dispersal and population structure at different spatial scales in the subterranean rodent Ctenomys australis
<p>Abstract</p> <p><b>Background</b></p> <p>The population genetic structure of subterranean rodent species is strongly affected by demographic (e.g. rates of dispersal and social structure) and stochastic factors (e.g. random genetic drift among subpopulations and habitat fragmentation). In particular, gene flow estimates at different spatial scales are essential to understand genetic differentiation among populations of a species living in a highly fragmented landscape. <it>Ctenomys australis </it>(the sand dune tuco-tuco) is a territorial subterranean rodent that inhabits a relatively secure, permanently sealed burrow system, occurring in sand dune habitats on the coastal landscape in the south-east of Buenos Aires province, Argentina. Currently, this habitat is threatened by urban development and forestry and, therefore, the survival of this endemic species is at risk. Here, we assess population genetic structure and patterns of dispersal among individuals of this species at different spatial scales using 8 polymorphic microsatellite loci. Furthermore, we evaluate the relative importance of sex and habitat configuration in modulating the dispersal patterns at these geographical scales.</p> <p>Results</p> <p>Our results show that dispersal in <it>C. australis </it>is not restricted at regional spatial scales (~ 4 km). Assignment tests revealed significant population substructure within the study area, providing support for the presence of two subpopulations from three original sampling sites. Finally, male-biased dispersal was found in the Western side of our study area, but in the Eastern side no apparent philopatric pattern was found, suggesting that in a more continuous habitat males might move longer distances than females.</p> <p>Conclusions</p> <p>Overall, the assignment-based approaches were able to detect population substructure at fine geographical scales. Additionally, the maintenance of a significant genetic structure at regional (~ 4 km) and small (less than 1 km) spatial scales despite apparently moderate to high levels of gene flow between local sampling sites could not be explained simply by the linear distance among them. On the whole, our results support the hypothesis that males disperse more frequently than females; however they do not provide support for strict philopatry within females.</p
Coulomb excitation of the mirror pair
Background: Electric-quadrupole () strengths relate to the underlying
quadrupole deformation of a nucleus and present a challenge for many nuclear
theories. Mirror nuclei in the vicinity of the line of represent a
convenient laboratory for testing deficiencies in such models, making use of
the isospin-symmetry of the systems. Purpose: Uncertainties associated with
literature strengths in \textsuperscript{23}Mg are some of the largest in
nuclei in the -shell. The purpose of the
present work is to improve the precision with which these values are known, to
enable better comparison with theoretical models. Methods: Coulomb-excitation
measurements of Mg and Na were performed at the TRIUMF-ISAC
facility using the TIGRESS spectrometer. They were used to determine the
matrix elements of mixed / transitions. Results: Reduced
transition strengths, , were extracted for \textsuperscript{23}Mg and
\textsuperscript{23}Na. Their precision was improved by factors of
approximately six for both isotopes, while agreeing within uncertainties with
previous measurements. Conclusions: A comparison was made with both shell-model
and {\it ab initio} valence-space in-medium similarity renormalization group
calculations. Valence-space in-medium similarity-renormalization-group
calculations were found to underpredict the absolute strength - in
agreement with previous studies
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