Foraging site selection of two subspecies of Bar-tailed Godwit Limosa lapponica:time minimizers accept greater predation danger than energy minimizers

Different spatial distributions of food abundance and predators may urge birds to make a trade-off between food intake and danger. Such a trade-off might be solved in different ways in migrant birds that either follow a time-minimizing or energy-minimizing strategy; these strategies have been assigned to two subspecies of Bar-tailed Godwits Limosa lapponica that use the European Wadden Sea during northward migration. At the study area on Terschelling, we recorded feeding site selection, time budgets and intake rates (prey/min) in the period that both lapponica (energy minimizer) and taymyrensis (time minimizer) subspecies were present (late April till the end of May 2007). Prey availability (number of prey/m2) was negatively correlated to the distance from cover. Based on sightings of colour-ringed Bar-tailed Godwits, taymyrensis was foraging closer to cover, and for a higher proportion of time than lapponica (67% vs. 33%). During the high tide period taymyrensis was also foraging on inland coastal meadows. Moreover, taymyrensis was more vigilant than lapponica, whereas lapponica showed more resting and preening behaviour. Lapponica had a higher instantaneous intake rate, but taymyrensis had a higher overall intake rate and the birds were more successful in taking larger prey items than lapponica. Supposedly, due to the increased foraging time and additional foraging on the inland meadows, the time-minimizing taymyrensis achieved a higher fuel deposition rate than lapponica. Taymyrensis shifted towards food-rich areas, apparently accepting higher predation risks, whereas energy-minimizing lapponica avoided predation danger by foraging further from cove

Risk factors for Lyme disease : A scale-dependent effect of host species diversity and a consistent negative effect of host phylogenetic diversity

Biodiversity can influence disease risk. One example of a diversity-disease relationship is the dilution effect, which suggests higher host species diversity (often indexed by species richness) reduces disease risk. While numerous studies support the dilution effect, its generality remains controversial. Most studies of diversity-disease relationships have overlooked the potential importance of phylogenetic diversity. Furthermore, most studies have tested diversity-disease relationships at one spatial scale, even though such relationships are likely scale dependent. Using Lyme disease as a model system, we investigated the effects of host species richness and phylogenetic relatedness on the number of reported Lyme disease cases in humans in the U.S.A. at two spatial scales (the county level and the state level) using piecewise structural equation modelling. We also accounted for relevant climatic and habitat-related factors and tested their correlations with the number of Lyme disease cases. We found that species assemblages with more related species (i.e., host species in the order Rodentia) were associated with more Lyme disease cases in humans. Host species richness correlated negatively with the number of Lyme disease cases at the state level (i.e., a dilution effect), a pattern that might be explained by the higher number of reservoir-incompetent species at high levels of species richness at this larger spatial scale. In contrast, a positive correlation was found between species richness and the number of Lyme disease cases at the county level, where a higher proportion of rodent species was associated with higher levels of species richness, potentially amplifying the disease risk. Our results highlight that analyse at a single spatial scale can miss some impacts of biodiversity on human health. Thus, multi-scale analyses with consideration of host phylogenetic diversity are critical for improving our understanding of diversity-disease relationships.Peer reviewe

Beyond Site-Specific Criteria: Conservation of Migratory Birds and Their Habitats from a Network Perspective

Many populations of birds depend on networks of sites to survive. Sufficient connectivity that allows movement between the sites throughout the year is a critical requirement. We found that existing international frameworks and policies for identifying sites important for bird conservation focus more at the level of the individual site than on the site network and its connectivity. Only 21% of site criteria acknowledge the importance of movement networks for birds, and such network criteria were mostly (67%) qualitative. We suggest a three-step quantitative approach for informing conservation about the connectivity of bird movements (especially when migrating) from a network perspective, by reviewing current scientific knowledge. The first step is to construct a bird movement network by identifying sites frequently used by birds as ‘nodes’, and then define ‘edges’ from the probability of non-stop flight between each pair of nodes. The second step is to quantify network connectivity, i.e., the extent to which the site network facilitates bird movements. The last step is to assess the importance of each site from its contribution to network connectivity. This approach can serve as a tool for comprehensive and dynamic monitoring of the robustness of site networks during global change

Beyond Site-Specific Criteria: Conservation of Migratory Birds and Their Habitats from a Network Perspective

Many populations of birds depend on networks of sites to survive. Sufficient connectivity that allows movement between the sites throughout the year is a critical requirement. We found that existing international frameworks and policies for identifying sites important for bird conservation focus more at the level of the individual site than on the site network and its connectivity. Only 21% of site criteria acknowledge the importance of movement networks for birds, and such network criteria were mostly (67%) qualitative. We suggest a three-step quantitative approach for informing conservation about the connectivity of bird movements (especially when migrating) from a network perspective, by reviewing current scientific knowledge. The first step is to construct a bird movement network by identifying sites frequently used by birds as ‘nodes’, and then define ‘edges’ from the probability of non-stop flight between each pair of nodes. The second step is to quantify network connectivity, i.e., the extent to which the site network facilitates bird movements. The last step is to assess the importance of each site from its contribution to network connectivity. This approach can serve as a tool for comprehensive and dynamic monitoring of the robustness of site networks during global change

Spatially heterogeneous shifts in vegetation phenology induced by climate change threaten the integrity of the avian migration network

Phenological responses to climate change frequently vary among trophic levels, which can result in increasing asynchrony between the peak energy requirements of consumers and the availability of resources. Migratory birds use multiple habitats with seasonal food resources along migration flyways. Spatially heterogeneous climate change could cause the phenology of food availability along the migration flyway to become desynchronized. Such heterogeneous shifts in food phenology could pose a challenge to migratory birds by reducing their opportunity for food availability along the migration path and consequently influencing their survival and reproduction. We develop a novel graph-based approach to quantify this problem and deploy it to evaluate the condition of the heterogeneous shifts in vegetation phenology for 16 migratory herbivorous waterfowl species in Asia. We show that climate change-induced heterogeneous shifts in vegetation phenology could cause a 12% loss of migration network integrity on average across all study species. Species that winter at relatively lower latitudes are subjected to a higher loss of integrity in their migration network. These findings highlight the susceptibility of migratory species to climate change. Our proposed methodological framework could be applied to migratory species in general to yield an accurate assessment of the exposure under climate change and help to identify actions for biodiversity conservation in the face of climate-related risks

The Dominant Source of CD4+ and CD8+ T-Cell Activation in HIV Infection Is Antigenic Stimulation

To distinguish between antigenic stimulation and CD4+ T-cell homeostasis as the cause of T-cell hyperactivation in HIV infection, we studied T-cell activation in 47 patients before and during highly active antiretroviral therapy (HAART). We show that expression of human leukocyte antigen (HLA)-DR, CD38, and Ki67 on T cells decreased during HAART but remained elevated over normal values until week 48 of therapy. We confirm previous reports that T-cell activation correlates positively with plasma HIV RNA levels (suggesting antigenic stimulation), and negatively with CD4 count (suggesting CD4+ T-cell homeostasis). However, these correlations may be spurious, because misleading, due to the well-established negative correlation between CD4 count and plasma HIV RNA levels. To resolve this conflict, we computed partial correlation coefficients. Correcting for CD4 counts, we show that plasma HIV RNA levels contributed to T-cell hyperactivation. Correcting for plasma HIV RNA levels, we show that CD4+ T-cell depletion contributed to T-cell activation. Correcting for both, activation of CD4+ and CD8+ T cells remained positively correlated. Because this suggests that CD4^+ and CD8^+ T-cell activation is caused by a common additional factor, we conclude that antigenic stimulation by HIV or other (opportunistic) infections is the most parsimonious explanation for T-cell activation in HIV infection. Persistence of HIV antigens may explain why T-cell activation fails to revert to levels found in healthy individuals after 48 weeks of therapy

Habitat loss exacerbates pathogen spread : An Agent-based model of avian influenza infection in migratory waterfowl

Habitat availability determines the distribution of migratory waterfowl along their flyway, which further influences the transmission and spatial spread of avian influenza viruses (ATVs). The extensive habitat loss in the East Asian-Australasian Flyway (EAAF) may have potentially altered the virus spread and transmission, but those consequences are rarely studied. We constructed 6 fall migration networks that differed in their level of habitat loss, wherein an increase in habitat loss resulted in smaller networks with fewer sites and links. We integrated an agent-based model and a susceptible-infected-recovered model to simulate waterfowl migration and AIV transmission. We found that extensive habitat loss in the EAAF can 1) relocate the outbreaks northwards, responding to the distribution changes of wintering waterfowl geese, 2) increase the outbreak risk in remaining sites due to larger goose congregations, and 3) facilitate AIV transmission in the migratory population. In addition, our modeling output was in line with the predictions from the concept of "migratory escape", i.e., the migration allows the geese to "escape" from the location where infection risk is high, affecting the pattern of infection prevalence in the waterfowl population. Our modeling shed light on the potential consequences of habitat loss in spreading and transmitting AIV at the flyway scale and suggested the driving mechanisms behind these effects, indicating the importance of conservation in changing spatial and temporal patterns of AIV outbreaks.Peer reviewe

Lorentz angle measurements in irradiated silicon detectors between 77 K and 300 K

Future experiments are using silicon detectors in a high radiation environment and in high magnetic fields. The radiation tolerance of silicon improves by cooling it to temperatures below 180 K. At low temperatures the mobility increases, which leads to larger de of the charge carriers by the Lorentz force. A good knowledge of the Lorentz angle is needed for design and operation of silicon detectors. We present measurements of the Lorentz angle between 77 K and 300 K before and after irradiation with a primary beam of 21 MeV protons

Renal Handling of Galectin-3 in the General Population, Chronic Heart Failure, and Hemodialysis

Background-Galectin-3 is a biomarker for prognostication and risk stratification of patients with heart failure (HF). It has been suggested that renal function strongly relates to galectin-3 levels. We aimed to describe galectin-3 renal handling in HF. Methods and Results-In Sprague-Dawley rats, we infused galectin-3 and studied distribution and renal clearance. Furthermore, galectin-3 was measured in urine and plasma of healthy controls, HF patients and hemodialysis patients. To mimic the human situation, we measured galectin-3 before and after the artificial kidney. Infusion in rats resulted in a clear increase in plasma and urine galectin-3. Plasma galectin-3 in HF patients (n=101; mean age 64 years; 93% male) was significantly higher compared to control subjects (n=20; mean age 58 years; 75% male) (16.6 ng/mL versus 9.7 ng/mL, P Conclusions-In this small cross-sectional study, we report that urine levels of galectin-3 are not increased in HF patients, despite substantially increased plasma galectin-3 levels. The impaired renal handling of galectin-3 in patients with HF may explain the described relation between renal function and galectin-3 and may account for the elevated plasma galectin-3 in HF