Interactions between land use,habitat use,and population increase in greater snow geese: what are the consequences for natural wetlands?

The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid‐1960s, average temperatures have increased by 1–2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing.     

Restoring Fire to Long-Unburned Pinus palustris Ecosystems: Novel Fire Effects and Consequences for Long-Unburned Ecosystems

Biologically rich savannas and woodlands dominated by Pinus palustris once dominated the southeastern U.S. landscape. With European settlement, fire suppression, and landscape fragmentation, this ecosystem has been reduced in area by 97%. Half of remnant forests are not burned with sufficient frequency, leading to declines in plant and animal species richness. For these fire‐suppressed ecosystems a major regional conservation goal has been ecological restoration, primarily through the reinitiation of historic fire regimes. Unfortunately, fire reintroduction in long‐unburned Longleaf pine stands can have novel, undesirable effects. We review case studies of Longleaf pine ecosystem restoration, highlighting novel fire behavior, patterns of tree mortality, and unintended outcomes resulting from reintroduction of fire. Many of these pineland restoration efforts have resulted in excessive overstory pine mortality (often >50%) and produced substantial quantities of noxious smoke. The most compelling mechanisms of high tree mortality after reintroduction of fire are related to smoldering combustion of surface layers of organic matter (duff) around the bases of old pines. Development of effective methods to reduce fuels and competing vegetation while encouraging native vegetation is a restoration challenge common to fire‐prone ecosystems worldwide that will require understanding of the responses of altered ecosystems to the resumption of historically natural disturbances.     

Scale-dependent climate signals drive breeding phenology of three seabird species

Breeding at the right time is essential for animals in seasonal climates in order to ensure that the energy demands of reproduction, particularly the nutritional requirements of growing young, coincide with peak food availability. Global climate change is likely to cause shifts in the timing of peak food availability, and in order to adapt successfully to current and future climate change, animals need to be able to adjust the time at which they initiate breeding. Many animals use environmental cues available before the breeding season to predict the seasonal peak in food availability and adjust their phenology accordingly. We tested the hypothesis that regulation of breeding onset should reflect the scale at which organisms perceive their environment by comparing phenology of three seabird species at a North Sea colony. As predicted, the phenology of two dispersive species, black-legged kittiwake ( Rissa tridactyla ) and common guillemot ( Uria aalge ), correlated with a large-scale environmental cue (the North Atlantic Oscillation), whereas a resident species, European shag ( Phalacrocorax aristotelis ), was more affected by local conditions (sea surface temperature) around the colony. Annual mean breeding success was lower in late years for European shags, but not for the other two species. Since correlations among climate patterns at different scales are likely to change in the future, these findings have important implications for how migratory animals can respond to future climate change.     

Prevalence and Seasonal Variations of Six Bee Viruses in Apis mellifera L. and Varroa destructor Mite Populations in France

A survey of six bee viruses on a large geographic scale was undertaken by using seemingly healthy bee colonies and the PCR technique. Samples of adult bees and pupae were collected from 36 apiaries in the spring, summer, and autumn during 2002. Varroa destructor samples were collected at the end of summer following acaricide treatment. In adult bees, during the year deformed wing virus (DWV) was found at least once in 97% of the apiaries, sacbrood virus (SBV) was found in 86% of the apiaries, chronic bee paralysis virus (CBPV) was found in 28% of the apiaries, acute bee paralysis virus (ABPV) was found in 58% of the apiaries, black queen cell virus (BQCV) was found in 86% of the apiaries, and Kashmir bee virus (KBV) was found in 17% of the apiaries. For pupae, the following frequencies were obtained: DWV, 94% of the apiaries; SBV, 80% of the apiaries; CBPV, none of the apiaries; ABPV, 23% of the apiaries; BQCV, 23% of the apiaries; and KBV, 6% of the apiaries. In Varroa samples, the following four viruses were identified: DWV (100% of the apiaries), SBV (45% of the apiaries), ABPV (36% of the apiaries), and KBV (5% of the apiaries). The latter findings support the putative role of mites in transmitting these viruses. Taken together, these data indicate that bee virus infections occur persistently in bee populations despite the lack of clinical signs, suggesting that colony disease outbreaks might result from environmental factors that lead to activation of viral replication in bees.     

Escherichia coli Constructs Expressing Human or Porcine Enterotoxins Induce Identical Diarrheal Diseases in a Piglet Infection Model

To develop a piglet model for studying diarrheal disease and developing vaccines, we challenged gnotobiotic piglets with isogenic Escherichia coli strains constructed to express porcine 987P(F6) fimbriae and a heat-labile or a heat-stable enterotoxin to examine clinical outcomes. Piglets developed identical diarrheal diseases when inoculated with constructs expressing human or porcine enterotoxins.     

Formation of Nanoscale Elemental Silver Particles via Enzymatic Reduction by Geobacter sulfurreducens

Geobacter sulfurreducens reduced Ag(I) (as insoluble AgCl or Ag⁺ ions), via a mechanism involving c-type cytochromes, precipitating extracellular nanoscale Ag(0). These results extend the range of metals known to be reduced by Geobacter species and offer a method for recovering silver from contaminated water as potentially useful silver nanoparticles.     

Solution structure of duplex DNA containing the mutagenic lesion 1,N(2)-etheno-2'-deoxyguanine

We have used high-resolution NMR spectroscopy and molecular dynamics simulations to determine the solution structure of DNA containing the genotoxic lesion 1, N (2)-etheno-2'-deoxyguanosine (epsilonG), paired to dC. The NMR data suggest the presence of a major, minimally perturbed structure at neutral pH. NOESY spectra indicate the presence of a right-handed helix with all nucleotides in anti, 2'-deoxyribose conformations within the C2'-endo/C1'-exo range and proper Watson-Crick base pair alignments outside the lesion site. The epsilonG residue remains deeply embedded inside the helix and stacks between the flanking base pairs. The lesion partner dC is extrahelical and is located in the minor groove of the duplex, where it is highly exposed to solvent. Upon acidification of the sample, a second conformation at the lesion site of the duplex emerges, with protonation of the lesion partner dC and possible formation of a Hoogsteen base pair. Restrained molecular dynamics simulations of the neutral-pH structure generated a set of three-dimensional models that show epsilonG inside the helix, where the lesion is stabilized by stacking interactions with flanking bases but without participating in hydrogen bonding. The lesion counterbase dC is displaced in the minor groove of the duplex where it can form a hydrogen bond with the sugar O4' atom of a residue 2 bp away.     

Proton-dependent electron transfer from CuA to heme a and altered EPR spectra in mutants close to heme a of cytochrome oxidase

Eukaryotic cytochrome c oxidase (CcO) and homologous prokaryotic forms of Rhodobacter and Paraccocus differ in the EPR spectrum of heme a. It was noted that a histidine ligand of heme a (H102) is hydrogen bonded to serine in Rhodobacter (S44) and Paraccocus CcOs, in contrast to glycine in the bovine enzyme. Mutation of S44 to glycine shifts the heme a EPR signal from g(z) = 2.82 to 2.86, closer to bovine heme a at 3.03, without modifying other properties. Mutation to aspartate, however, results in an oppositely shifted and split heme a EPR signal of g(z) = 2.72/2.78, accompanied by lower activity and drastically inhibited intrinsic electron transfer from CuA to heme a. This intrinsic rate is biphasic; the proportion that is slow is pH dependent, as is the relative intensity of the two EPR signal components. At pH 8, the heme a EPR signal at 2.72 is most intense, and the electron transfer rate (CuA to heme a) is 10-130 s(-1), compared to wild-type at 90,000 s(-1). At pH 5.5, the signal at 2.78 is intensified, and a biphasic rate is observed, 50% fast (approximately wild type) and 50% slow (90 s(-1)). The data support the prediction that the hydrogen-bonding partner of the histidine ligand of heme a is one determinant of the EPR spectral difference between bovine and bacterial CcO. We further demonstrate that the heme a redox potential can be dramatically altered by a nearby carboxyl, whose protonation leads to a proton-coupled electron transfer process.