Effects of environmental conditions on reproductive effort and nest success of Arctic‐breeding shorebirds

The Arctic is experiencing rapidly warming conditions, increasing predator abundance, and diminishing population cycles of keystone species such as lemmings. However, it is still not known how many Arctic animals will respond to a changing climate with altered trophic interactions. We studied clutch size, incubation duration and nest survival of 17 taxa of Arctic‐breeding shorebirds at 16 field sites over 7 years. We predicted that physiological benefits of higher temperatures and earlier snowmelt would increase reproductive effort and nest survival, and we expected increasing predator abundance and decreasing abundance of alternative prey (arvicoline rodents) to have a negative effect on reproduction. Although we observed wide ranges of conditions during our study, we found no effects of covariates on reproductive traits in 12 of 17 taxa. In the remaining taxa, most relationships agreed with our predictions. Earlier snowmelt increased the probability of laying a full clutch from 0.61 to 0.91 for Western Sandpipers, and shortened incubation by 1.42 days for arcticola Dunlin and 0.77 days for Red Phalaropes. Higher temperatures increased the probability of a full clutch from 0.60 to 0.93 for Western Sandpipers and from 0.76 to 0.97 for Red‐necked Phalaropes, and increased daily nest survival rates from 0.9634 to 0.9890 for Semipalmated Sandpipers and 0.9546 to 0.9880 for Western Sandpipers. Higher abundance of predators (foxes) reduced daily nest survival rates only in Western Sandpipers (0.9821–0.9031). In contrast to our predictions, the probability of a full clutch was lowest (0.83) for Semipalmated Sandpipers at moderate abundance of alternative prey, rather than low abundance (0.90). Our findings suggest that in the short‐term, climate warming may have neutral or positive effects on the nesting cycle of most Arctic‐breeding shorebirds.     

Compatibility of a natural enemy, Coleomegilla maculata lengi (Col., Coccinellidae) and four insecticides used against the Colorado potato beetle (Col., Chrysomelidae)

Abstract:   The toxicity of four insecticides used to control the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), imidacloprid (Admire^®), cryolite (Kryocide^®), cyromazine (Trigard^®), and Bacillus thuringiensis var. tenebrionis (Novodor^®), to one of its natural enemies, the 12-spotted lady beetle, Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae) was determined in the laboratory. Toxicity assays against C. maculata adults and larvae consisted of (1) topical applications and (2) exposures to treated foliage and prey, using concentrations up to 10 times the manufacturer's recommendations. Over a 6-day period, cyromazine (insect growth regulator) and B. t . var. tenebrionis (microbial insecticide) had no lethal effects on first and third instars C. maculata . For both larval and adult stages, cryolite (inorganic insecticide) caused very low predator mortality when topically applied and moderate mortality when ingested through contaminated eggs of Colorado potato beetles. Imidacloprid (systemic organic insecticide) was highly toxic to adult and larval C. maculata . Its estimated LD₅₀ at 6 days following treatment, corresponded to 0.02–0.09 times the recommended field concentration, depending on the developmental stage and mode of contamination. These results indicate that integrated pest management programmes for Colorado potato beetles using imidacloprid or, to a lesser degree, cryolite, would be detrimental to C. maculata . Cyromazine and B. t . var. tenebrionis seem to present a better compatibility with the protection of C. maculata populations.     

Hordoindolines are associated with a major endosperm-texture QTL in barley (Hordeum vulgare).

Endosperm texture has a tremendous impact on the end-use quality of wheat (Triticum aestivum L.). Cultivars of barley (Hordeum vulgare L.), a close relative of wheat, also vary measurably in grain hardness. However, in contrast to wheat, little is known about the genetic control of barley grain hardness. Puroindolines are endosperm-specific proteins found in wheat and its relatives. In wheat, puroindoline sequence variation controls the majority of wheat grain texture variation. Hordoindolines, the puroindoline homologs of barley, have been identified and mapped. Recently, substantial allelic variation was found for hordoindolines among commercial barley cultivars. Our objective was to determine the influence of hordoindoline allelic variation upon grain hardness and dry matter digestibility in the 'Steptoe' x 'Morex' mapping population. This population is segregating for hordoindoline allele type, which was measured by a HinA/HinB/Gsp composite marker. One-hundred and fifty lines of the 'Steptoe' x 'Morex' population were grown in a replicated field trial. Grain hardness was estimated by near-infrared reflectance (NIR) and measured using the single kernel characterization system (SKCS). Variation attributable to the HinA/HinB/Gsp locus averaged 5.7 SKCS hardness units (SKCS U). QTL analysis revealed the presence of several areas of the genome associated with grain hardness. The largest QTL mapped to the HinA/HinB/Gsp region on the short arm of chomosome 7 (5H). This QTL explains 22% of the SKCS hardness difference observed in this study. The results indicate that the Hardness locus is present in barley and implicates the hordoindolines in endosperm texture control.     

Field Metabolic Rate Is Dependent on Time-Activity Budget in Ring-Billed Gulls (Larus delawarensis) Breeding in an Anthropogenic Environment

Environmental and behavioral factors have long been assumed to affect variation in avian field metabolic rate (FMR). However, due to the difficulties in measuring continuous behavior of birds over prolonged periods of time, complete time-activity budgets have rarely been examined in relation to FMR. Our objective was to determine the effect of activity (measured by detailed time-activity budgets) and a series of extrinsic and intrinsic factors on FMR of the omnivorous ring-billed gull (Larus delawarensis). The experiment was conducted during the incubation period when both members of the pair alternate between attending the nest-site and leaving the colony to forage in aquatic and anthropogenic environments (city, agricultural). FMR was determined using the doubly labeled water method. Time-activity budgets were extrapolated from spatio-temporal data (2-5 days) obtained from bird-borne GPS data loggers. Gulls had low FMRs compared to those predicted by allometric equations based on recorded FMRs from several seabird species. Gulls proportioned their time mainly to nest-site attendance (71% of total tracking time), which reduced FMR/g body mass, and was the best variable explaining energy expenditure. The next best variable was the duration of foraging trips, which increased FMR/g; FMR/g was also elevated by the proportion of time spent foraging or flying (17% and 8% of tracking time respectively). Most environmental variables measured did not impact FMR/g, however, the percent of time birds were subjected to temperatures below their lower critical temperature increased FMR. Time-activity budgets varied between the sexes, and with temperature and capture date suggesting that these variables indirectly affected FMR/g. The gulls foraged preferentially in anthropogenic-related habitats, which may have contributed to their low FMR/g due to the high availability of protein- and lipid-rich foods. This study demonstrates that activities were the best predictors of FMR/g in ring-billed gulls, thus providing strong support for this long-standing theory in bioenergetics.     

Inactivation mechanism of tetrameric beta-galactosidase by gamma-rays involves both fragmentation and temperature-dependent denaturation of protomers

The radiation inactivation method is widely used to estimate the molecular size of membrane-bound enzymes, receptors, and transport systems in situ. The method is based on the principle that exposure of frozen solutions or lyophilized protein preparations to increasing doses of ionizing radiations results in a first-order decay of biological activity proportional to radiation inactivation size of the protein. This parameter is believed to reflect the "functional unit" of the protein defined as the minimal assembly of structure (protomers) required for expression of a given biological activity. We tested the functional unit as a concept to interpret radiation inactivation data of proteins with Escherichia coli beta-galactosidase, where the protomers are active only when associated in a tetramer. Gamma-Irradiation of beta-galactosidase at both -78 and 38 degrees C followed by quantitation of the residual unfragmented promoter band by SDS-polyacrylamide gel electrophoresis yielded the protomer size, indicating that only one protomer is fragmented by each radiation hit. By following the enzyme activity as a function of dose it was found that only the protomer that has been directly hit and fragmented at -78 degrees C was effectively inactivated. In contrast, at 38 degrees C, it was the whole tetramer that was inactivated. beta-Galactosidase cannot have two different functional units depending on temperature. The inactivation of the whole beta-galactosidase tetramer at 38 degrees C is in fact related to protomer fragmentation but also to the production of stable denatured protomers (detected by gel-filtration HPLC and differential UV spectroscopy) due to energy transfer from fragmented protomers toward unhit protomers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Solid-phase analogue synthesis of caspase-3 inhibitors via palladium-catalyzed amination of 3-bromopyrazinones

Caspase-3 is a cysteinyl protease that mediates apoptotic cell death. Its inhibition may have an important impact on the treatment of several degenerative diseases. Here we report the synthesis of reversible inhibitors via a solid-support palladium-catalyzed amination of 3-bromopyrazinones and the discovery of a pan-caspase reversible inhibitor.     

Mapping and sequence analysis of barley hordoindolines

Barley (Hordeum vulgare L.) cultivars vary in traits such as grain hardness and malt quality. However, little is known about the genetic basis of these grain quality traits in barley, while more is known about the basis of grain hardness in wheat (Triticum aestivum L.). Puroindolines are endosperm-specific proteins found in wheat and barley, as well as other members of the Triticeae. In wheat, variation of puroindoline sequence is associated with most of the variability in wheat grain texture. However, no information exists on sequence variation of the barley homologs of puroindolines, the hordoindolines. We have therefore chosen to isolate and characterize the hordoindoline (hin) sequences of eight North American barley cultivars. The barley sequences contain numerous non-conservative amino-acid substitutions relative to their wheat counterparts. However, no significant rearrangements were found in either hinA or hinB of barley. Three hinA and two hinB sequence types were found among the eight barley cultivars examined, indicating substantial allelic variation at this locus. The hinB sequence variability was used to map hinB to the short arm of chromosome 5H in a Steptoe/Morex mapping population, which is coincident with the previously mapped location of hinA and Gsp (grain-softness protein). This chromosomal location also coincides with a small barley malt-extract QTL, suggesting that hordoindoline sequence variation may play a small role in barley grain quality. Efforts to correlate barley seed textural differences and malting quality with hordoindoline sequence type are ongoing. Received: 25 May 2000 / Accepted: 21 September 2000     

Reliability of Quality Assessments in Research Synthesis: Securing the Highest Quality Bioinformation for HIT

Current trends in bio-medicine include research synthesis and dissemination of bioinformation by means of health (bio)information technology (H[b] IT). Research must secure the validity and reliability of assessment tools to quantify research qualityin the pursuit of the best available evidence. Our concerted work in this domain led to the revision of three instruments for thatpurpose, including the stringent characterization of inter-rater reliability and coefficient of agreement. It is timely and critical toadvance the methodological development of the science of research synthesis by strengthening the reliability of existing measure ofresearch quality in order to ensure H[b] IT efficacy and effectiveness.     

Are goose nesting success and lemming cycles linked? Interplay between nest density and predators

The suggested link between lemming cycles and reproductive success of arctic birds is caused by potential effects of varying predation pressure (the Alternative Prey Hypothesis, APH) and protective association with birds of prey (the Nesting Association Hypothesis, NAH). We used data collected over two complete lemming cycles to investigate how fluctuations in lemming density were associated with nesting success of greater snow geese ( Anser caerulescens atlanticus ) in the Canadian High Arctic. We tested predictions of the APH and NAH for geese breeding at low and high densities. Goose nesting success varied from 22% to 91% between years and the main egg predator was the arctic fox ( Alopex lagopus ). Nesting associations with snowy owls ( Nyctea scandiaca ) were observed but only during peak lemming years for geese nesting at low density. Goose nesting success declined as distance from owls increased and reached a plateau at 550 m. Artificial nest experiments indicated that owls can exclude predators from the vicinity of their nests and thus reduce goose egg predation rate. Annual nest failure rate was negatively associated with rodent abundance and was generally highest in low lemming years. This relationship was present even after excluding goose nests under the protective influence of owls. However, nest failure was inversely density-dependent at high breeding density. Thus, annual variations in nest density influenced the synchrony between lemming cycles and oscillations in nesting success. Our results suggest that APH is the main mechanism linking lemming cycles and goose nesting success and that nesting associations during peak lemming years (NAH) can enhance this positive link at the local level. The study also shows that breeding strategies used by birds (the alternative prey) could affect the synchrony between oscillations in avian reproductive success and rodent cycles.     

Maize genes encoding the small subunit of ADP-glucose pyrophosphorylase

Plant ADP-glucose pyrophosphorylase (AGP) is a heterotetrameric enzyme composed of two large and two small subunits. Here, we report the structures of the maize (Zea mays) genes encoding AGP small subunits of leaf and endosperm. Excluding exon 1, protein-encoding sequences of the two genes are nearly identical. Exon 1 coding sequences, however, possess no similarity. Introns are placed in identical positions and exhibit obvious sequence similarity. Size differences are primarily due to insertions and duplications, hallmarks of transposable element visitation. Comparison of the maize genes with other plant AGP small subunit genes leads to a number of noteworthy inferences concerning the evolution of these genes. The small subunit gene can be divided into two modules. One module, encompassing all coding information except that derived from exon 1, displays striking similarity among all genes. It is surprising that members from eudicots form one group, whereas those from cereals form a second group. This implies that the duplications giving rise to family members occurred at least twice and after the separation of eudicots and monocot cereals. One intron within this module may have had a transposon origin. A different evolutionary history is suggested for exon 1. These sequences define three distinct groups, two of which come from cereal seeds. This distinction likely has functional significance because cereal endosperm AGPs are cytosolic, whereas all other forms appear to be plastid localized. Finally, whereas barley (Hordeum vulgare) reportedly employs only one gene to encode the small subunit of the seed and leaf, maize utilizes the two genes described here.