bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geographical segregation in DunlinCalidris alpinapopulations wintering along the East Atlantic migratory flyway – evidence from mitochondrial DNA analysis
Authors: Lopes Ricardo J. , Hortas Francisco , Wennerberg Liv 
Published: October 2008

ABSTRACTDunlinCalidris alpinais one of the most abundant shorebirds using coastal habitats in the East Atlantic migratory flyway, that links arctic breeding locations (Greenland to Siberia) with wintering grounds (West Europe to West Africa). Differential migration and winter segregation between populations have been indicated by morphometrics and ringing recoveries. Here, we analyse the potential of genetic markers (mitochondrial DNA – mtDNA) to validate and enhance such findings. We compared mtDNA haplotypes frequencies at different wintering sites (from north‐west Europe to West Africa). All birds from West Africa had western (European) haplotypes, while the eastern (Siberian) haplotypes were only present in European winter samples, reaching higher frequencies further north in Europe. Compilation of published results from migrating birds also confirmed these differences, with the sole presence of European haplotypes in Iberia and West Africa and increasingly higher frequencies of Siberian haplotypes from south‐west to north‐west Europe. Comparison with published haplotype frequencies of breeding populations shows that birds from Greenland, Iceland, and North Europe were predominant in wintering grounds in West Africa, while populations wintering in West Europe originated from more eastern breeding grounds (e.g. North Russia). These results show that genetic markers can be used to enhance the integrative monitoring of wintering and breeding populations, by providing biogeographical evidence that validate the winter segregation of breeding populations.
Effects of sample size on the performance of species distribution models
Authors: Wisz M. S. , Hijmans R. J. , Li J. , Peterson A. T. , Graham C. H. , Guisan A. ,   NCEAS Predicting Species Distributions Working Group
Published: October 2008

ABSTRACTA wide range of modelling algorithms is used by ecologists, conservation practitioners, and others to predict species ranges from point locality data. Unfortunately, the amount of data available is limited for many taxa and regions, making it essential to quantify the sensitivity of these algorithms to sample size. This is the first study to address this need by rigorously evaluating a broad suite of algorithms with independent presence–absence data from multiple species and regions. We evaluated predictions from 12 algorithms for 46 species (from six different regions of the world) at three sample sizes (100, 30, and 10 records). We used data from natural history collections to run the models, and evaluated the quality of model predictions with area under the receiver operating characteristic curve (AUC). With decreasing sample size, model accuracy decreased and variability increased across species and between models. Novel modelling methods that incorporate both interactions between predictor variables and complex response shapes (i.e. GBM, MARS‐INT, BRUTO) performed better than most methods at large sample sizes but not at the smallest sample sizes. Other algorithms were much less sensitive to sample size, including an algorithm based on maximum entropy (MAXENT) that had among the best predictive power across all sample sizes. Relative to other algorithms, a distance metric algorithm (DOMAIN) and a genetic algorithm (OM‐GARP) had intermediate performance at the largest sample size and among the best performance at the lowest sample size. No algorithm predicted consistently well with small sample size (n < 30) and this should encourage highly conservative use of predictions based on small sample size and restrict their use to exploratory modelling.
Understanding population structure and historical demography in a conservation context: population genetics of an endangered fern
Authors: Kang Ming , Huang Hongwen , Jiang Mingxi , Lowe Andrew J. 
Published: October 2008

ABSTRACTThe construction of the world's largest hydroelectric scheme across the Yangtze River, the Three Gorges Dams (TGD), in the centre of a southern‐central Chinese biodiversity hot spot, the Three Gorges Reservoir Area (TGRA), has attracted international concern and conservation action. To examine whether landscape changes to date have impacted regional flora, and to establish long‐term monitoring baselines, we assessed the distribution and dynamics of an endangered and TGRA endemic fern, Adiantum reniforme var. sinense. For eight nuclear microsatellites, high levels of genetic diversity (HE = 0.653–0.781) and slightly elevated inbreeding (FIS = 0.077–0.197) were found across 13 surveyed populations. The population history of this fern is characterized by a balance of gene flow and genetic drift, where historical dispersal, inferred from coalescent (F = 0.129) and genetic differentiation (FST = 0.094 and RST = 0.180) approaches, is moderate, reflecting an isolation by distance relationship. Importantly, most populations exhibited mutation‐drift disequilibrium, suggesting a recent population decline, which is congruent with the known demographic history of the species following dam‐related activities. Based on these results, populations of A. reniforme var. sinense are expected to lose genetic diversity and increase genetic structure as dam‐related activities decrease size and increase genetic isolation of remnants.
Phylogeography of the widespread marine invader Microcosmus squamiger (Ascidiacea) reveals high genetic diversity of introduced populations and non‐independent colonizations
Authors: Rius Marc , Pascual Marta , Turon Xavier 
Published: October 2008

ABSTRACTThe spread of non‐indigenous species into new marine habitats represents an increasing threat to global diversity. Genetic techniques provide basic understanding of the invasion processes. The ascidian Microcosmus squamiger is considered to be native to Australia, having been spread worldwide via transoceanic vessels. It has successfully invaded artificial and natural habitats where it has become a pest. We studied phylogeography and genetic structure of 12 M. squamiger populations, including samples from its native range (Australia) and introduced populations from the Indian, Pacific, and Atlantic oceans, as well as the Mediterranean Sea. We amplified 574 bp of the mitochondrial COI gene in 258 individuals and found a total of 52 haplotypes. A haplotype tree revealed two main groups of haplotypes. The relative frequency of each group of haplotypes, multidimensional scaling, and analysis of molecular variance showed important differences between the western Australia localities and the remaining ones (eastern Australia and introduced populations). Furthermore, we found that the colonization of the different areas by M. squamiger has not occurred independently, as many introduced populations shared some low frequency alleles. A nested clade analysis showed a global pattern of restricted gene flow with isolation by distance, although we found episodes of long‐distance dispersal in some clades. A contiguous range expansion was detected between Australian populations. We conclude that M. squamiger is native to Australia and has most likely expanded its range of distribution sequentially through worldwide shipping, especially from the harbours of the more populated eastern Australia. In introduced populations, we found a high genetic diversity which suggests enhanced invasive potential. Consequently, there is a need to control this species, as it outcompetes local biota and is an economic threat.
Modelling invasion for a habitat generalist and a specialist plant species
Authors: Evangelista Paul H. , Kumar Sunil , Stohlgren Thomas J. , Jarnevich Catherine S. , Crall Alycia W. , Norman III John B. , Barnett David T. 
Published: October 2008

ABSTRACTPredicting suitable habitat and the potential distribution of invasive species is a high priority for resource managers and systems ecologists. Most models are designed to identify habitat characteristics that define the ecological niche of a species with little consideration to individual species’ traits. We tested five commonly used modelling methods on two invasive plant species, the habitat generalist Bromus tectorum and habitat specialist Tamarix chinensis, to compare model performances, evaluate predictability, and relate results to distribution traits associated with each species. Most of the tested models performed similarly for each species; however, the generalist species proved to be more difficult to predict than the specialist species. The highest area under the receiver‐operating characteristic curve values with independent validation data sets of B. tectorum and T. chinensis was 0.503 and 0.885, respectively. Similarly, a confusion matrix for B. tectorum had the highest overall accuracy of 55%, while the overall accuracy for T. chinensis was 85%. Models for the generalist species had varying performances, poor evaluations, and inconsistent results. This may be a result of a generalist's capability to persist in a wide range of environmental conditions that are not easily defined by the data, independent variables or model design. Models for the specialist species had consistently strong performances, high evaluations, and similar results among different model applications. This is likely a consequence of the specialist's requirement for explicit environmental resources and ecological barriers that are easily defined by predictive models. Although defining new invaders as generalist or specialist species can be challenging, model performances and evaluations may provide valuable information on a species’ potential invasiveness.
No positive correlation between species and genetic diversity in European alpine grasslands dominated by Carex curvula
Authors: Puşcaş Mihai , Taberlet Pierre , Choler Philippe 
Published: October 2008

ABSTRACTThe distributional range of alpine plants experienced dramatic changes during the Quaternary ice ages. These changes offer many opportunities for studying the impact of habitat contraction and fragmentation on both species and genetic diversity. Here, we examined the amplified fragment length polymorphism‐based genetic diversity in the sedge Carex curvula All. in relation to the species diversity of siliceous European alpine grasslands in which the sedge is dominant. We found no relationship or even a negative relationship between genetic and species diversity indices. Local species richness was associated with the regional pool size of siliceous alpine species, which was itself dependent on the extant area of suitable habitats for these species. Genetic diversity of C. curvula was primarily shaped by the presumed location of glacial refugia and the routes of post‐glacial colonization. We conclude that the two levels of diversity are not positively correlated because genotypes and species do not respond similarly to the spatial dynamics of suitable habitats induced by Quaternary temperature changes.
Impacts of a woody invader vary in different vegetation communities
Authors: Mason T. J. , French K. 
Published: October 2008

AbstractThe impact of an exotic species in natural systems may be dependent not only on invader attributes but also on characteristics of the invaded community. We examined impacts of the invader bitou bush, Chrysanthemoides monilifera ssp. rotundata, in fore and hind dune communities of coastal New South Wales, Australia. We compared invader impacts on vegetation structure, richness of both native and exotic growth forms and community variability in fore and hind dunes. We found that impacts of bitou invasion were context specific: in fore dune shrublands, functionally distinct graminoid, herb and climber rather than shrub growth forms had significantly reduced species richness following bitou invasion. However, in forested hind dunes, the functionally similar native shrub growth form had significantly reduced species richness following bitou invasion. Density of vegetation structure increased at the shrub level in both fore and hind dune invaded communities compared with non‐invaded communities. Fore dune ground‐level vegetation density declined at invaded sites compared with non‐invaded sites, reflecting significant reductions in herb and graminoid species richness. Hind dune canopy‐level vegetation density was reduced at invaded compared with non‐invaded sites. Bitou bush invasion also affected fore dune community variability with significant increases in variability of species abundances observed in invaded compared with non‐invaded sites. In contrast, variability among all hind dune sites was similar. The results suggest that effects of bitou bush invasion are mediated by the vegetation community. When bitou bush becomes abundant, community structure and functioning may be compromised.
Seed supply, drought, and grazing determine spatio‐temporal patterns of recruitment for native and introduced invasive pines in grasslands
Authors: Boulant Nadine , Kunstler Georges , Rambal Serge , Lepart Jacques 
Published: October 2008

ABSTRACTAim The rate of grassland invasion by trees depends on the ability of the species to invade, i.e. their invasiveness, and on the susceptibility of the environments to invasion, i.e. their invasibility. Knowledge of the invasiveness of native and introduced tree species and of the environmental factors that contribute to invasibility is necessary to understand landscape evolution and assess required management measures. Our main aim was to explore this by estimating the separate effects of propagule pressure and environmental factors on the spatio‐temporal patterns of sapling recruitment, a key stage in the tree life cycle.Location Causse Mejean calcareous plateau (southern France).Methods The effects of seed supply and environmental variables (grazing, geological substrate, and duration or intensity of drought) on the spatio‐temporal patterns of sapling recruitment were assessed for the native Scots pine (Pinus sylvestrisL.) and the introduced black pine (Pinus nigraArn. ssp.nigra). Estimates were derived by inverse modelling with data of locations and ages of 4‐ to 20‐year‐old saplings and seed‐bearing trees in 32 sites. Yearly indices of drought were derived from a soil–water content model.Results For both species, seed supply was as important as the whole set of environmental factors in explaining sapling recruitment rates. Grazing and the duration of drought from July to August decreased sapling recruitment rates, which were also lower on hard limestone than on dolomite. Dispersal distances and effective fecundities were higher for the introducedP. nigra, which was less susceptible to drought but more affected by grazing than the nativeP. sylvestris. In grazed grasslands, shrubs facilitated sapling establishment of both species.Main conclusions This study shows how seed supply and environmental factors shape spatio‐temporal patterns of sapling recruitment for trees invading grasslands. Implications for landscape evolution and management, of the difference in invasiveness of the two pine species and of the hierarchy of environmental factors in determining invasibility, are discussed.
Advances in Tunneled Central Venous Catheters for Dialysis: Design and Performance
Authors: Ash Stephen R. 
Published: October 2008

AbstractOver 70% of patients initiating chronic hemodialysis in the United States have a tunneled central venous catheter (CVC) for dialysis as their first blood access device. Tunneled CVC have requirements that are unparalleled by other access devices: high blood flow rates at moderate pressure drops without obstruction, minimal trauma to the vein, resistance to occlusion by fibrous sheathing, prevention of infection, avoidance of clotting, biocompatibility, avoidance of lumen collapse and kinking and breaks, resistance to antiseptic agents, placement with minimal trauma, and radiopaque appearance on X‐ray. This publication reviews the numerous designs for tunneled CVC and evaluates the advantages and disadvantages of each design. A catheter that self‐centers in the superior vena cava (Centros™) is described, along with early clinical results. Current challenges and future directions for tunneled CVC for dialysis are discussed, included means to diminish catheter‐related infections, catheter tip clotting, fibrous sheathing, central venous stenosis, and external component bulk.
Hemodialysis Central Venous Catheter Dysfunction
Authors: Chan Micah R. 
Published: October 2008

AbstractDespite aggressive efforts to increase autogenous fistula prevalence, catheters remain an essential access modality to a large percentage of the hemodialysis population. Central venous catheter dysfunction, which includes catheter‐related bacteremia and thrombotic occlusion, comprises the majority of complications which affect dialysis adequacy, patient quality of life, patient survival, and the economics of health care. This review provides a comprehensive overview of hemodialysis central venous catheter dysfunction, its epidemiology and risk factors, and avenues of prevention and treatment. Novel directions for future investigation are also addressed.
Infection Associated with Tunneled Hemodialysis Catheters
Authors: Beathard Gerald A. , Urbanes Aris 
Published: October 2008

AbstractThe use of tunneled dialysis catheters to deliver hemodialysis treatment may be associated with major problems. For this reason their use should be minimized as much as possible. Infection is the most serious of these problems. This complication causes very significant morbidity and mortality and has emerged as the primary barrier to long‐term catheter use. Bacteremia is the most serious type of infection associated with catheter use. It can result in metastatic infection and even lead to death of the patient. Prophylaxis is important to decrease the risk of infection. The use of an antibiotic ointment at the exit site until it has healed and the long‐term use of a dressing to cover the exit site are effective in decreasing the incidence of exit‐site infection. With optimal catheter‐use management, it should be possible to reduce the incidence of catheter‐related bacteremia (CRB) to a level in the range of 1/1000 catheter days. Antibiotic and antimicrobial locking solutions show promise and may, if verified in appropriate clinical studies, prove to be important adjuncts to the management of catheter‐dependent patients. Aspirin has been shown to have anti‐staphylococcal activity and warrants further clinical evaluation. The diagnosis of CRB is based upon positive blood cultures in association with typical clinical features. If a simple routine blood culture is positive, along with a high clinical probability based upon the patient’s signs and symptoms, the sensitivity and specificity of the diagnosis is greater than 75%. CRB is in reality a biofilm infection and must be treated as such. Treatment needs to focus on appropriate systemic antibiotics which should be continued for a minimum of 3 weeks and catheter management to remove the biofilm. Catheter exchange has been shown to be effective and should be performed based upon the clinical presentation of the patient. While treatment with a combination of systemic antibiotics and antibiotic locking solution may be effective for gram‐negative infections, this approach does not appear to be a good choice for Staphylococcus aureus CRB.
Surface‐Treated Catheters—A Review
Authors: Dwyer Amy 
Published: October 2008

AbstractAlmost 30% of prevalent hemodialysis patients use catheters for vascular access although outcomes are superior with the use of either an arteriovenous fistula or a synthetic graft. Catheter complications are a major cause of morbidity and mortality for hemodialysis patients and increase the burden on the health care system. Surface‐treated catheters have been developed to combat the three most common causes of catheter failure: infection, fibrin sheath formation, and thrombus formation. Two types of catheter surface treatments are available: antimicrobial coatings and antithrombotic coatings. Surface treatment of central venous catheters with antimicrobial materials reduces both bacterial colonization and the incidence of catheter‐related bacteremia in critical care patients by 30–50%. Antithrombotic coatings reduce platelet adhesion, inhibit the inflammatory response, and reduce thrombus formation on coronary stents, ventricular assist devices, central venous catheters, and vascular grafts. However, few reports on the use of surface‐treated catheters in the chronic hemodialysis patient population exist. At the present time, it is difficult to justify the increased cost of surface‐treated catheters for chronic hemodialysis in the absence of clinical data demonstrating that they reduce catheter‐related complications in this patient population.
Catheter‐Related Mortality among ESRD Patients
Authors: Wasse Haimanot 
Published: October 2008

AbstractHemodialysis access‐related complications remain one of the most important sources of morbidity and cost among persons with end‐stage renal disease, with total annual costs exceeding $1 billion annually. In this context, the creation and maintenance of an effective hemodialysis vascular access is essential for safe and adequate hemodialysis therapy. Multiple reports have documented the type of vascular access used for dialysis and associated risk of infection and mortality. Undoubtedly, the central venous catheter (CVC) is associated with the greatest risk of infection‐related and all‐cause mortality compared with the autogenous arteriovenous fistula (AVF) or synthetic graft (AVG). The AVF has the lowest risk of infection, longer patency rates, greater quality of life, and lower all‐cause mortality compared with the AVG or CVC. It is for these reasons that the National Kidney Foundation’s Kidney Disease Outcome Quality Initiative Clinical Practice Guidelines for Vascular Access recommend the early placement and use of the AVF among at least 50% of incident hemodialysis patients. This report presents catheter‐related mortality and calls for heightened awareness of catheter‐related complications.
High‐Resolution Ultrasound Elasticity Imaging to Evaluate Dialysis Fistula Stenosis
Authors: Weitzel William F. , Kim Kang , Park Dae Woo , Hamilton James , O’Donnell Matthew , Cichonski Thomas J. , Rubin Jonathan M. 
Published: October 2008

AbstractAccurate, noninvasive characterization of arterial wall mechanics and detection of fibrotic vascular lesions could vastly improve the ability to predict patient response to local treatments such as angioplasty. Current imaging and other techniques for determining wall compliance rely on imprecise or indirect estimates of wall motion. This study used high‐resolution ultrasound imaging with phase‐sensitive speckle tracking to obtain detailed and direct measurements of arterial stiffness in two subjects with dialysis fistula dysfunction. In both subjects, the absolute values of strain were much higher in normal regions of fistula than in regions of stenosis. The lower values of strain in stenotic fistula indicate greater stiffness of the vessel wall. The ultrasound speckle tracking technique used here may have potential to determine vascular mechanical properties noninvasively with a level of precision and accuracy not currently available.