53 research outputs found
Distribution of Breeding Shorebirds on the Arctic Coastal Plain of Alaska
Available information on the distribution of breeding shorebirds across the Arctic Coastal Plain of Alaska is dated, fragmented, and limited in scope. Herein, we describe the distribution of 19 shorebird species from data gathered at 407 study plots between 1998 and 2004. This information was collected using a single-visit rapid area search technique during territory establishment and early incubation periods, a time when social displays and vocalizations make the birds highly detectable. We describe the presence or absence of each species, as well as overall numbers of species, providing a regional perspective on shorebird distribution. We compare and contrast our shorebird distribution maps to those of prior studies and describe prominent patterns of shorebird distribution. Our examination of how shorebird distribution and numbers of species varied both latitudinally and longitudinally across the Arctic Coastal Plain of Alaska indicated that most shorebird species occur more frequently in the Beaufort Coastal Plain ecoregion (i.e., closer to the coast) than in the Brooks Foothills ecoregion (i.e., farther inland). Furthermore, the occurrence of several species indicated substantial longitudinal directionality. Species richness at surveyed sites was highest in the western portion of the Beaufort Coastal Plain ecoregion. The broad-scale distribution information we present here is valuable for evaluating potential effects of human development and climate change on Arctic-breeding shorebird populations.Les renseignements qui existent en matiĂšre de rĂ©partition des oiseaux de rivage en reproduction sur la plaine cĂŽtiĂšre de lâArctique en Alaska sont anciens, fragmentĂ©s et restreints. Ici, nous dĂ©crivons la rĂ©partition de 19 espĂšces dâoiseaux de rivage Ă partir de donnĂ©es recueillies Ă 407 lieux de recherche entre 1998 et 2004. Cette information a Ă©tĂ© recueillie grĂące Ă une technique de recherche consistant en une seule visite rapide durant les pĂ©riodes dâĂ©tablissement du territoire et de dĂ©but dâincubation, pĂ©riodes pendant lesquelles les comportements sociaux et les vocalisations permettent de bien repĂ©rer les oiseaux. Nous dĂ©crivons la prĂ©sence ou lâabsence de chaque espĂšce, de mĂȘme que le nombre gĂ©nĂ©ral dâespĂšces, ce qui procure une perspective rĂ©gionale de la rĂ©partition des oiseaux de rivage. Nous comparons et contrastons nos cartes de rĂ©partition des oiseaux de rivage Ă celles dâĂ©tudes antĂ©rieures, en plus de dĂ©crire les tendances les plus marquĂ©es en matiĂšre de rĂ©partition des oiseaux de rivage. Notre examen de la variation latitudinale et longitudinale en matiĂšre de rĂ©partition et de nombre dâespĂšces dâoiseaux de rivage Ă lâĂ©chelle de la plaine cĂŽtiĂšre arctique de lâAlaska nous a permis de constater que la plupart des espĂšces dâoiseaux de rivage se manifestaient plus souvent dans la rĂ©gion Ă©cologique de la plaine cĂŽtiĂšre de Beaufort (câest-Ă -dire plus proche de la cĂŽte) que dans la rĂ©gion Ă©cologique des contreforts de Brooks (câest-Ă -dire plus Ă lâintĂ©rieur des terres). Par ailleurs, lâoccurrence de plusieurs espĂšces indiquait une directionalitĂ© longitudinale substantielle. La richesse des espĂšces aux sites Ă lâĂ©tude Ă©tait Ă son meilleur dans la partie ouest de la rĂ©gion Ă©cologique de la plaine cĂŽtiĂšre de Beaufort. Les renseignements sur la rĂ©partition Ă grande Ă©chelle que nous prĂ©sentons ici jouent un rĂŽle dans lâĂ©valuation des effets Ă©ventuels des travaux de mise en valeur par lâĂȘtre humain et du changement climatique sur les populations dâoiseaux de rivage en reproduction de lâArctique
Predictors of invertebrate biomass and rate of advancement of invertebrate phenology across eight sites in the North American Arctic
Average annual temperatures in the Arctic increased by 2â3 °C during the second half of the twentieth century. Because
shorebirds initiate northward migration to Arctic nesting sites based on cues at distant wintering grounds, climate-driven
changes in the phenology of Arctic invertebrates may lead to a mismatch between the nutritional demands of shorebirds
and the invertebrate prey essential for egg formation and subsequent chick survival. To explore the environmental drivers
afecting invertebrate availability, we modeled the biomass of invertebrates captured in modifed Malaise-pitfall traps over
three summers at eight Arctic Shorebird Demographics Network sites as a function of accumulated degree-days and other
weather variables. To assess climate-driven changes in invertebrate phenology, we used data from the nearest long-term
weather stations to hindcast invertebrate availability over 63 summers, 1950â2012. Our results confrmed the importance
of both accumulated and daily temperatures as predictors of invertebrate availability while also showing that wind speed
negatively afected invertebrate availability at the majority of sites. Additionally, our results suggest that seasonal prey avail ability for Arctic shorebirds is occurring earlier and that the potential for trophic mismatch is greatest at the northernmost
sites, where hindcast invertebrate phenology advanced by approximately 1â2.5 days per decade. Phenological mismatch
could have long-term population-level efects on shorebird species that are unable to adjust their breeding schedules to the
increasingly earlier invertebrate phenologies.publishedVersio
Expression in Aneuploid Drosophila S2 Cells
Analysis of the relationship between gene copy number and gene expression in aneuploid male Drosophila cells reveals a global compensation mechanism in addition to X chromosome-specific dosage compensation
Transcriptional Profiling of Human Liver Identifies Sex-Biased Genes Associated with Polygenic Dyslipidemia and Coronary Artery Disease
Sex-differences in human liver gene expression were characterized on a genome-wide scale using a large liver sample collection, allowing for detection of small expression differences with high statistical power. 1,249 sex-biased genes were identified, 70% showing higher expression in females. Chromosomal bias was apparent, with female-biased genes enriched on chrX and male-biased genes enriched on chrY and chr19, where 11 male-biased zinc-finger KRAB-repressor domain genes are distributed in six clusters. Top biological functions and diseases significantly enriched in sex-biased genes include transcription, chromatin organization and modification, sexual reproduction, lipid metabolism and cardiovascular disease. Notably, sex-biased genes are enriched at loci associated with polygenic dyslipidemia and coronary artery disease in genome-wide association studies. Moreover, of the 8 sex-biased genes at these loci, 4 have been directly linked to monogenic disorders of lipid metabolism and show an expression profile in females (elevated expression of ABCA1, APOA5 and LDLR; reduced expression of LIPC) that is consistent with the lower female risk of coronary artery disease. Female-biased expression was also observed for CYP7A1, which is activated by drugs used to treat hypercholesterolemia. Several sex-biased drug-metabolizing enzyme genes were identified, including members of the CYP, UGT, GPX and ALDH families. Half of 879 mouse orthologs, including many genes of lipid metabolism and homeostasis, show growth hormone-regulated sex-biased expression in mouse liver, suggesting growth hormone might play a similar regulatory role in human liver. Finally, the evolutionary rate of protein coding regions for human-mouse orthologs, revealed by dN/dS ratio, is significantly higher for genes showing the same sex-bias in both species than for non-sex-biased genes. These findings establish that human hepatic sex differences are widespread and affect diverse cell metabolic processes, and may help explain sex differences in lipid profiles associated with sex differential risk of coronary artery disease
Mechanisms and Evolutionary Patterns of Mammalian and Avian Dosage Compensation
A large-scale comparative gene expression study reveals the different ways in which the chromosome-wide gene dosage reductions resulting from sex chromosome differentiation events were compensated during mammalian and avian evolution
Extended Thromboprophylaxis with Betrixaban in Acutely Ill Medical Patients
Background
Patients with acute medical illnesses are at prolonged risk for venous thrombosis. However, the appropriate duration of thromboprophylaxis remains unknown.
Methods
Patients who were hospitalized for acute medical illnesses were randomly assigned to receive subcutaneous enoxaparin (at a dose of 40 mg once daily) for 10±4 days plus oral betrixaban placebo for 35 to 42 days or subcutaneous enoxaparin placebo for 10±4 days plus oral betrixaban (at a dose of 80 mg once daily) for 35 to 42 days. We performed sequential analyses in three prespecified, progressively inclusive cohorts: patients with an elevated d-dimer level (cohort 1), patients with an elevated d-dimer level or an age of at least 75 years (cohort 2), and all the enrolled patients (overall population cohort). The statistical analysis plan specified that if the between-group difference in any analysis in this sequence was not significant, the other analyses would be considered exploratory. The primary efficacy outcome was a composite of asymptomatic proximal deep-vein thrombosis and symptomatic venous thromboembolism. The principal safety outcome was major bleeding.
Results
A total of 7513 patients underwent randomization. In cohort 1, the primary efficacy outcome occurred in 6.9% of patients receiving betrixaban and 8.5% receiving enoxaparin (relative risk in the betrixaban group, 0.81; 95% confidence interval [CI], 0.65 to 1.00; P=0.054). The rates were 5.6% and 7.1%, respectively (relative risk, 0.80; 95% CI, 0.66 to 0.98; P=0.03) in cohort 2 and 5.3% and 7.0% (relative risk, 0.76; 95% CI, 0.63 to 0.92; P=0.006) in the overall population. (The last two analyses were considered to be exploratory owing to the result in cohort 1.) In the overall population, major bleeding occurred in 0.7% of the betrixaban group and 0.6% of the enoxaparin group (relative risk, 1.19; 95% CI, 0.67 to 2.12; P=0.55).
Conclusions
Among acutely ill medical patients with an elevated d-dimer level, there was no significant difference between extended-duration betrixaban and a standard regimen of enoxaparin in the prespecified primary efficacy outcome. However, prespecified exploratory analyses provided evidence suggesting a benefit for betrixaban in the two larger cohorts. (Funded by Portola Pharmaceuticals; APEX ClinicalTrials.gov number, NCT01583218. opens in new tab.
Unexpected diversity in socially synchronized rhythms of shorebirds
The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1, 5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parentâs incubation bout varied from 1â19âh, whereas period lengthâthe time in which a parentâs probability to incubate cycles once between its highest and lowest valueâvaried from 6â43âh. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h lightâdark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms
Seasonal variation in California bighorn ram (Ovis canadensis californiana) habitat use and group size
Seasonal changes in bighorn sheep (Ovis canadensis) habitat use and social systems can create profound management challenges. We studied spring-summer distribution, habitat use, and group size of California bighorn rams on Poker Jim Ridge, Oregon. Ram groups were observed during April-August 1990. Herd range was smaller in spring (24.4 km2) than summer (74.5 km2). Ram groups were closer to escape terrain (P< 0.001), farther from water (P < 0.001), on gentler slopes (P = 0.01) and at higher elevations (P < 0.001) in spring. Distance to escape terrain and distance to water were significant main effects differentiating spring and summer habitat use (P < 0.001). Rain group size varied by month (P < 0.001), with groups in July-August smaller than those in April-June (P < 0.01). Seasonal changes in ram distribution appeared to be associated with changing habitat conditions, particularly water availability. Small group sizes in late summer probably reflected resource limitations, and occurred in spite of use of less secure habitats during this period. Managers of bighorn sheep populations should consider the unique requirements of their populations under a variety of environmental conditions, and provide adequate protection to sustain seasonal shifts in distributionPayer and Coblentz "Seasonal variation in California bighorn ram (Ovis canadensis californiana) habitat use and group size." Northwest Science. 1997; 71(4): 281-28
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