Quantifying rates of random mating in western corn rootworm emerging from Cry3Bb1‐expressing and refuge maize in field cages

The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is the most significant pest of field maize, Zea mays L. (Poaceae), in the USA. Maize plants expressing Bt toxins targeting the corn rootworm complex have been widely adopted and are the primary insecticidal control measure for this pest in North America. Insect resistance management tactics using various refuge structures have been adopted to ensure Bt products will retain durability. An assumption of the refuge strategy is that males and females emerging from Bt and refuge plantings mate randomly; this has not been tested in the field. We conducted cage studies using field populations of WCR in Indiana, USA, to generate empirical field data on mating rates between beetles emerging from Cry3Bb1‐expressing Bt and refuge maize plants. Two refuge configurations were tested; all refuge plants were labeled using the stable isotope ¹⁵N. This mark persists in adult beetles after eclosion, allowing for collection and analysis of isotopic ratios of all beetles. Additional data collected included adult emergence rates, timing and sex ratios for each of the treatments, and head capsule size and dry weights of beetles collected. Treatment had a significant effect on dry weight; mean dry weight decreased in Bt‐only treatments. Fisher's exact test of proportions of mating pairs of refuge and Bt insects indicated that mating was not random in 20% strip refuges and 5% seed blend treatments. We found high percentages of beetles that fed on Bt‐expressing plants as larvae, suggesting that mating between resistant beetles may not be rare even if random mating did occur.     

崖爬藤的生态生物学特征及其扦插繁殖技术

崖爬藤为葡萄科常绿或半常绿藤本,具有重要园林绿化价值。该研究采用叶片离析法和石蜡切片法研究其叶片的形态结构。结果表明:崖爬藤平均叶面积(23.1 cm~2)较大,单位叶面积干重(4.4 mg·cm~(-2))较小,成熟叶厚约为195.5μm,栅栏组织不发达,胞间隙大。利用便携式LI-6400光合测定仪、PAM-2100荧光测定仪对崖爬藤光合生理生态指标进行研究。结果表明:其PSⅡ的最大光化学效率Fv/Fm(0.818)较高;叶片的净光合速率日变化呈单峰型,没有明显的光合午休现象,最大净光合速率Pn为3.691μmol·m~(-2)·s~(-1),出现在14:00时,变化趋势与光合有效辐射Par、大气温度T、蒸腾速率Tr、气孔导度Gs等因子相同,与胞间CO_2浓度Ci相反,同时具有较高的水分利用效率(3.056μmol·mmol~(-1))。这都显示了崖爬藤喜阴湿环境,不耐寒且具有一定的耐旱特性,适合栽植于我国温度较高的南方地区。此外,以崖爬藤1~2年生老枝和当年生嫩枝为材料,经梯度溶液IBA处理进行扦插生根实验,结果表明,崖爬藤扦插繁殖迅速,生根率较高,以当年生嫩枝不经IBA处理直接扦插为最佳。该研究结果将为崖爬藤的栽培及开发利用提供重要的理论和技术指导。     

Re-establishment of dominance by dwarf shrubs on grass heaths

Experimental fields were established at three sites on different soil types in Dutch heathlands, where grass species have become dominant, in order to find methods for re-establishment of an ericoid dwarf-shrub heath. Treatments included mowing, mowing and cutting for hay, ploughing, milling, sod cutting and burning.Re-establishment of ericoid dwarf shrubs was only observed after creation of gaps or patches of open soil. The results after nine years for two of the sites and six years for the other site indicate that sod cutting is the most suitable method provided that the mineral top soil is not removed or disturbed. More profound removal of the sod including mineral soil causes a delay in re-establishment of ericoid dwarf shrubs and an increase of grasses.Factors that may explain different responses to gap creation including availability of seeds, soil moisture, soil fertility and plant survival strategies are briefly discussed.Abbreviations Calluna = Calluna vulgaris - Deschampsia = Deschampsia flexuosa - Erica = Erica tetralix - Molinia = Molinia caerulea - Sarothammus = Sarothammus scoparius     

Soil processes and sulfate loss at the Hubbard Brook Experimental Forest

The Hubbard Brook Ecosystem Study was designed to evaluate element flux and cycling in a northern hardwood forest and the effects of disturbance on these processes. In the original experiment, an entire watershed was deforested and regrowth was inhibited for three years using herbicides. Initial effects of the treatment included: elevated stream discharge, large increases in streamwater solute concentrations and elevated losses of those ions from the watershed. In contrast, streamwater concentrations and net ecosystem output of sulfate decreased in response to the treatment. During the post treatment period, the concentrations of most dissolved ions declined relative to a reference watershed while, again in contrast, sulfate concentrations increased relative to the reference. In this paper we develop a hypothesis which links acidification and sulfate adsorption processes in the soil to explain the observed trends in sulfate losses from the Hubbard Brook Experimental Forest.     

Sediment chemistry of lakes formed by surface-mining for coal in the midwestern U.S.A.

Sediment from lakes on abandoned coal mines in the Midwestern U.S.A. was examined to determine the factors controlling chemical composition and the role the sediment plays in lake neutralization. Sediment concentrations of many cations, (especially heavy metals) are strongly correlated with sediment sulfide concentration, but poorly correlated with the pH of the overlying water. Leaching the sediment of one lake with 1 N ammonium acetate, 0.1 N HCl, and 6 N HCl revealed that cations were mostly bound in weak acid-leachable and strong acid-leachable forms. The weak acid-leachable form is likely to be metal sulfides and calcium carbonate. The sulfide-poor sediments of extremely acid lakes contained few weak acid-leachable cations. Raw mine-spoil contained large amounts of easily leached cations. There is little relationship between changes in sediment chemistry over time determined from cores of lake sediment and past lake pH. Rates of sulfide deposition were examined in sediment cores because sulfate reduction and deposition has been suggested as a major source of alkalinity in lakes influenced by acid precipitation. Although the rate of sulfate deposition in surface mine lakes is high, it alone seems to be insufficient to cause neutralization.     

Using scissors to quantify hardness of insects: do bats select for size or hardness?

Scissors are used to determine the hardness of fresh insects of different size and taxa. Our results indicate a strong relationship between the size of an insect and its hardness, which can be expressed as log( F _max)=0.65 × log( V )+ α . F _max is the maximal force needed to cut the insect and is our measure of insect hardness. V is the volume of the insect and α is a constant that can be derived for different insect taxa. The value of 0.65 was found as an average of beetle and moth samples, and this number appears consistent across insect taxa. We found that beetles averaged about 3.2 times harder than moths of the same size. Beetles were also more variable in hardness than moths, with the softest beetles about equal in hardness to an average moth of the same size. Using our data on insect hardness coupled with data on the diets of bats and their bite forces from the literature, we attempt to determine whether the upper size limit of insects taken by a bat is limited by the insect's dimensions or its hardness. Our results indicate that both these factors may be important.     

Survival of Salmonella on refrigerated chicken carcasses and subsequent transfer to cutting board

Objective:  To determine the effect of refrigeration time and temperature on Salmonella cell numbers on inoculated chicken carcasses and their transfer to a plastic cutting board.
Methods and Results:  The survival of Salmonella on chicken skin and the transfer to a plastic cutting board when exposed to different refrigeration temperatures (2, 6 or 8°C) for 9 days were the two main issues on which this work focused. Two scenarios were carried out to ascertain these effects: carcasses treated with a decontaminating acetic acid solution and untreated carcasses. All of the contaminated carcasses remained contaminated after 9 days of refrigeration. However, on untreated samples, while Salmonella numbers increased almost 1·5 log at 8°C, the pathogen numbers decreased about 1 log at 2 and 6°C. On acid-treated samples, cell numbers slightly decreased at all of the temperatures studied. Temperature did not affect salmonellae transfer to the cutting board, but time did. Acid decontamination increased cell numbers transferred to the cutting board compared with untreated samples.
Conclusion:  Proper refrigeration at low temperatures did not allow Salmonella numbers to rise, regardless of which carcasses had been, or had not been, acid treated. Despite the fact that the rate of transfer was not affected by temperature, the acid treatment detached Salmonella cells from the chicken skin and, therefore, the probability of greater cross-contamination should be studied further.
Significance and Impact of the Study:  The results of this study may provide better information about the refrigeration conditions for fresh chicken storage and also determine if these, along with acetic acid decontamination of broiler chicken, would affect the pathogen transfer to a cutting board.     

The vesicular-arbuscular (VA) mycorrhiza and its effects on growth of vegetatively propagated Theobroma cacao L.

A greenhouse experiment was conducted to study the effects of mycorrhizal inoculation on growth and nutrient uptake of vegetatively propagated cocoa plants from the Sabah hybrid (NA 33 × PA 7) raised on unsterilized Munchong soils. Inoculation with mixed species of Scutellospora and Glomus, resulted in higher dry matter yield and stem diameter of mycorrhizal plants obtained through budding, air layering or marcotting (a form of asexual plant propagation using vegetative parts and the selection of a healthy branch and scraping off the bark at the lower end of the branch, forcing it to root by covering it with a ball of soil) and stem cutting. Budded and marcotted mycorrhizal plants gave a significant increase in P content of shoots. In contrast, only budded mycorrhizal plants (on both young and old rootstocks) gave a significantly higher Ca concentration in tops, compared to uninoculated plants.     

Using strip seeding to test how restoration design affects randomness of community assembly

The reestablishment and enhancement of plant diversity is typically a priority for restoration practitioners. Since diversity and stability can be affected by the magnitude to which randomness drives community dynamics, modifying randomness (via habitat heterogeneity) could provide utility for vegetation managers. We investigated the value of using strip seeding to manipulate the magnitude to which randomness structures plant communities across a grassland in Davis, California. Five years after restoring portions of a degraded site (0, 33, 50, 66, and 100% of an area) to create patches of seeded and unseeded strips, we assessed the amount of Jaccard dissimilarity across quadrats within strips and estimated the magnitude to which randomness contributed to community assembly (termed the nugget). We found higher nuggets in the 66 and 33% seeding treatment levels compared to the 0, 50, and 100% seeding treatment levels. In the 33 and 66% level of the seeding treatment, we also found that unseeded strips, which are regularly exposed to random events of dispersal from seeded strips, had a higher nugget than seeded strips. This work suggests that strategic seeding techniques that enhance habitat heterogeneity can increase the role of randomness in community dynamics. Strip seeding strategies appear to provide utility as a tool to indirectly enhance diversity across a degraded site.