Condition-dependent response to changes in pollen stores by honey bee (Apis mellifera) colonies with different parasitic loads

The impact of a parasitic infestation may be influenced by nutritional state, in both individuals and colonies. This study examined the interaction between pollen storage and the effects of an infestation by the mite, Varroa jacobsoni Oudemans, in colonies of the honey bee, Apis mellifera L. We manipulated the pollen storage and mite infestation levels of colonies, and measured pollen foraging and brood rearing. Increased pollen stores decreased both the number of pollen foragers and pollen load size, while initially at least foragers from colonies with moderate infestations carried smaller pollen loads than those from lightly infested colonies. Over the course of the experiment, all colonies significantly increased pollen-foraging rates and pollen consumption, which was presumably a seasonal effect. Lightly infested colonies exhibited a larger increase in pollen forager number than moderately infested colonies, suggesting that more intense mite infestations compromised forager recruitment. Brood production was not affected by the addition of pollen, but moderately infested colonies were rearing significantly less brood by the end of the experiment than lightly infested colonies. Furthermore, the efficiency with which colonies converted pollen to brood decreased as the pollen storage level decreased and the infestation level increased. The results of this study may indicate that honey bee colonies adaptively alter brood-production efficiency in response to parasitic infestations and seasonal changes. Received: 3 May 1999 / Received in revised form: 14 September 1999 / Accepted: 25 September 1999     

Selection on worker honeybee responses to queen pheromone (Apis mellifera L.)

 Disruptive selection for responsiveness to queen mandibular gland pheromone (QMP) in the retinue bioassay resulted in the production of high and low QMP responding strains of honeybees (Apis mellifera L.). Strains differed significantly in their retinue response to QMP after one generation of selection. By the third generation the high strain was on average at least nine times more responsive than the low strain. The strains showed seasonal phenotypic plasticity such that both strains were more responsive to the pheromone in the spring than in the fall. Directional selection for low seasonal variation indicated that phenotypic plasticity was an additional genetic component to retinue response to QMP. Selection for high and low retinue responsiveness to QMP was not an artifact of the synthetic blend because both strains were equally responsive or non-responsive to whole mandibular gland extracts compared with QMP. The use of these strains clearly pointed to an extra-mandibular source of retinue pheromones (Pankiw et al. 1995; Slessor et al. 1998; Keeling et al. 1999). Received: 2 March 2000 / Accepted in revised form: 4 September 2000     

Climatic/edaphic controls on soil carbon/nitrogen response to shrub encroachment in desert grassland.

The proliferation of woody plants in grasslands over the past 100+ years can alter carbon, nitrogen, and water cycles and influence land surface-atmosphere interactions. Although the majority of organic carbon in these ecosystems resides belowground, there is no consensus on how this change in land cover has affected soil organic carbon (SOC) and total nitrogen (TN) pools. The degree to which duration of woody plant occupation, climate, and edaphic conditions have mediated SOC and TN responses to changes in life-form composition are poorly understood. We addressed these issues at a desert grassland site in Arizona, USA, where the leguminous shrub velvet mesquite (Prosopis velutina) has proliferated along an elevation/precipitation/temperature gradient and on contrasting soil morphologic surfaces. On sandy loam complexes of mid-Holocene origin, mean SOC and TN of soils in the grassland matrix increased approximately 68% and approximately 45%, respectively, with increasing elevation. Soil organic carbon pools were comparable and TN pools were approximately 23% higher in Pleistocene-aged clay loam complexes co-occurring with Holocene-aged soils at the upper elevation/climatic zone. Across the site, belowground resources associated with large Prosopis plants were 21-154% (SOC) and 18-127% (TN) higher than those in the grassy matrix. The variance in SOC and TN pools accounted for by Prosopis stem size (a rough surrogate for time of site occupation) was highest at the low- and mid-elevation sites (69-74%) and lowest at the upper elevation site (32-38%). Soil delta15N values ranged from 5.5 per thousand to 6.7 per thousand across the soil/elevation zones but were comparable in herbaceous and shrub-impacted soils and exhibited a weak relationship with Prosopis basal stem diameter (r2 < 0.1) and TN (r2 < 0.08). The SOC delta13C values decreased linearly with increasing Prosopis basal diameter, suggesting that size and isotopic composition of the SOC pool is a function of time of Prosopis site occupation. Isotopic mixture models indicate that encroachment of C3 woody plants has also promoted SOC additions from C4 plant sources, indicative of long-term herbaceous facilitation. Grassy sites in contrasting soil/elevation combinations, initially highly distinctive in their SOC pool size and delta13C, appear to be converging on similar values following approximately 100 years of woody plant proliferation.     

Assessing Conservation Value Using Centers of Population Density

We present an index of centers of density for identifying areas of high conservation value. This index represents the average importance of an area to species occurring there as measured by comparisons of relative densities of each species among areas. We evaluated the index using collections of stream fishes from the Clinch River system above Norris Reservoir in Virginia and Tennessee (U.S.A.). A strong correlation between index values measured at the same sites at different times suggested that the index could be applied to sites without replicated samples in the region and still allow centers of density to be distinguished from noncenters. Species richness showed no relationship to the index, suggesting that conservation priorities based solely on species richness can be inadequate. A species-accumulation curve based on the index performed nearly as well as one based on an algorithm for identifying the minimum number of sites in which all species in the region are represented. This pattern reflected the tendency of the index to weight regionally rare species more heavily than common species. But sites with high index values were not necessarily those selected by the algorithm because the algorithm used only presence/absence, whereas the index used the additional information present in relative densities. Our index represents an additional tool for identifying "hot spots" of diversity, but conservation of biodiversity over the long term will also require that the ecological integrity of regional landscape be maintained.     

Fuel Economy and Motor Vehicle Emissions

The conventional wisdom is that there is no relationship between fuel economy and motor vehicle emissions, at least for new cars. The requirement that all vehicles meet a common emission standard in terms of grams per mile effectively breaks whatever link there might have been between fuel economy and emissions in uncontrolled (preregulatory) vehicles. As cars age, however, the emission control equipment tends to break down, providing reason to think that the conventional wisdom might do the same. This paper reports on an empirical examination of this proposition, by linking EPA fuel economy certification data to a large database of motor vehicle emission measurements collected by remote sensing. It is found that better fuel economy is strongly associated with lower emissions of CO and HC and that the effect gets stronger as vehicles age.     

Short-Term Nitrogen Dioxide Exposure and Acute Respiratory Disease in Children

A CHESS data base from Chattanooga, Tennessee was thoroughly scrutinized and found to be of high enough quality to warrant epidemiological analysis. Using this data base, the relationship between NO₂ ambient pollution levels and acute respiratory disease in children was examined. Although a statistically significant relationship was found, it was not monotonic. Indeed, over the range of pollution values experiences, more illness is associated with low pollution values than with high ones. A U-shaped relationship between illness and NO₂ concentrations was found in several subpopulations in addition to the entire data set, although for some subpopulations no relationship was found. In contrast, higher ambient sulfate levels were found to have a positive effect on acute respiratory disease incidence in children over the entire period and for different subsamples, although this effect was not significant for either season analyzed separately.     

Child passenger injury risk in motor vehicle crashes: a comparison of nighttime and daytime driving by teenage and adult drivers

INTRODUCTION: To examine the association between child passenger injury risk, restraint use, and crash time (day vs. night) for children in crashes of vehicles driven by teenage versus adult drivers. METHODS: Cross-sectional study involving telephone interviews with insured drivers in a probability sample of 6,184 crashes involving 10,028 children. RESULTS: Child passengers in teen nighttime crashes had an increased injury risk and an increased risk of restraint nonuse compared with those in teen daytime crashes. This increased injury risk can be explained by differences in the age of child passengers, collision type, and child passenger's restraint status associated with time of day. CONCLUSIONS: In order to limit the risk of injury to child passengers driven by teens, Graduated Driver Licensing (GDL) laws should include provisions restricting nighttime driving, as well as mandates for age-appropriate restraint for child passengers. Consideration should also be given for education in child passenger safety for novice teen drivers as part of the licensing process. IMPACT ON INDUSTRY: Results of this study can be used to support advocacy efforts by the automotive industry and others to promote nighttime driving restrictions on novice drivers. In addition, given that both driver groups were more likely to be involved in a single-vehicle collision during the night, technologies such as electronic stability control may offer opportunities for protection. Further reseach on specific circumstances of teen nighttime crashes is needed to inform industry efforts to improve visibility or vehicle operation under poor lighting conditions.     

First application of preimplantation genetic diagnosis to neurofibromatosis type 2 (NF2)

Neurofibromatosis type 2 (NF2) is a dominantly inherited cancer predisposition syndrome that is caused bymutations in the NF2 gene. We report here the first clinical preimplantation genetic diagnosis (PGD) forNF2. A protocol was developed to simultaneously amplify the mutation and a single nucleotide polymorphism (SNP) located within the gene. The mutation and polymorphism were analysed by simultaneous fluorescent single-strand conformation polymorphism (SSCP) on an automated DNA sequencer. The mutation, carried by the male partner, was a single base pair substitution affecting a splice site in intron 4 of the gene. The female partner was infertile due to polycystic ovary syndrome and would require IVF to conceive. The couple was found to be informative at a linked intragenic SNP situated in the 5′ untranslated region of the gene. The SNP was included in the assay to reduce the risk of misdiagnosis due to allele dropout (ADO). The couple underwent three cycles of treatment during which a total of 43 blastomeres were biopsied from 31 embryos. Amplification at both loci was obtained in 35 cells (81%). A total of five embryos were transferred, two in the first cycle, two in the second and one in the third. No pregnancy ensued. The results of the diagnoses indicated that, in this couple, the inheritance of the mutation may be non-Mendelian. Out of a total of 32 embryos tested only four were found not to carry the mutation. The reasons for this apparent skew remain unknown. Copyright © 2002 John Wiley & Sons, Ltd.     

Hybrid Bottom Line: another perspective on the sustainability of organizations

In recent years, there has been a growing concern and an increasing number of proactive initiatives from various stakeholders on issues related to the environment, social matters, and economic aspects and this has been the main driving force toward sustainability. However, most players that are deeply involved with environmental and social agendas indicate that these actions have been more of a temporary palliative for the current unsustainability problems than real structural solutions, especially in what concerns the relationship between short-term actions and long-term structural planning. Even though the general literature on sustainability is comprehensive, there is a paucity of papers which look at it at the organizational level, and under a cross-sectoral perspective. This paper is an attempt to address this gap. It presents the concept of ‘Hybrid Bottom Line’ as a new perspective in understanding and sustainability at the organizational level.     

A diagnostic comparison of measured and model-predicted speciated VOC concentrations

This study compares speciated model-predicted concentrations (i.e., mixing ratios) of volatile organic compounds (VOCs) with measurements from the Photochemical Assessment Monitoring Stations (PAMS) network at sites within the northeastern US during June–August of 2006. Measurements of total non-methane organic compounds (NMOC), ozone (O₃), oxides of nitrogen (NO_x) and reactive nitrogen species (NO_y) are used for supporting analysis. The measured VOC species were grouped into the surrogate classes used by the Carbon Bond IV (CB4) chemical mechanism. It was found that the model typically over-predicted all the CB4 VOC species, except isoprene, which might be linked to overestimated emissions. Even with over-predictions in the CB4 VOC species, model performance for daily maximum O₃ was typically within ±15%. Analysis at an urban site in NY, where both NMOC and NO_x data were available, suggested that the reasonable ozone performance may be possibly due to compensating overestimated NO_x concentrations, thus modulating the NMOC/NO_x ratio to be in similar ranges as that of observations.