Towards defining aquatic ecosystem health for the Great Lakes

The Canada — U.S. Great Lakes Water Quality Agreement defines Areas of Concern as geographic areas that fail to meet the general or specific objectives of the Great Lakes Water Quality Agreement where such failure has caused or is likely to cause impairment of beneficial use or the area's ability to support aquatic life. Impairment of beneficial use is defined by the Agreement as a change in the physical, chemical or biological integrity sufficient to cause any one of 14 designated use impairments. In 1987 the International Joint Commission's Great Lakes Water Quality Board (GLWQB) recommended that criteria be developed to determine when ecosystem conditions have been impacted enough to warrant designation as an Area of Concern and when conditions have improved sufficiently to be delisted. Based on scientific input and policy considerations, the GLWQB adopted, in principle, a set of quantitative and qualitative listing/delisting criteria for each of the 14 use impairments. These criteria can be uniformly applied throughout the basin. Further, the GLWQB recommended future refinement of these criteria based on advances in science and public input.     

Disruptive Sublethal Effects of Insecticides on Biological Control: Altered Foraging Ability and Life Span of a Parasitoid after Feeding on Extrafloral Nectar of Cotton Treated with Systemic Insecticides

Predictions in integrated pest management on the compatibility of an insecticide with biological control often are based on incomplete screening tests. While measuring levels of mortality from direct insecticide exposure is a very common screening method, possible sublethal effects as a result of either direct or indirect insecticide exposure remain relatively unknown. The impact of sublethal effects on the success of biological control can be as deleterious as mortality. Here, we report the reduced host foraging ability and longevity of the parasitoid Microplitis croceipes Cresson (Hymenoptera: Braconidae) after feeding on extrafloral nectar from cotton (Gossypium hirsutum L., Malvaceae) plants that were treated with systemic insecticides. The insecticides used in this study are regularly applied in cotton-growing areas in the United States. For all tested insecticides, longevity of M. croceipes females that fed on nectar from cotton was affected for at least 10 days after plants were treated with insecticides. Moreover, the parasitoid's host foraging ability was severely affected for periods ranging from 2 days (imidacloprid) to 18 days (aldicarb) after insecticide application. The consequences of these sublethal effects on the success of biological control are discussed.     

Adaptation of experimental yeast populations to stressful conditions in relation to population size

The purpose of this experiment was to find out how a population becomes adapted to extremely stressful conditions as its environment deteriorates. We created a deteriorating environment for experimental selection lines of yeast by a stepwise increase in the concentration of salt in the growth medium. After each step, we tested the ability of the lines to grow at a high concentration of salt near the lethal limit for the ancestral strain. We found that mutations enhancing growth in this highly stressful environment began to spread at intermediate salt concentrations. The degree of enhancement was related to effective population size by a power law with a small exponent. The effect size of these mutations also increased with the population size in a similar fashion. From these results, we interpret adaptation to lethal stress as an indirect response to selection for resistance to previous lower levels of stress in a deteriorating environment. This suggests that the pattern of genetic correlation between successively higher levels of stress is an important factor in facilitating evolutionary rescue.     

Intermediate fragmentation surrounding vineyards favours the Coleoptera community within the crop

1. Insects of the order Coleoptera play an essential role in agricultural sustainability by supporting many ecosystem services (such as biological control, nutrient cycling or pollination). In agroecosystems, the Coleoptera community may be influenced by the surrounding landscape, which can provide living resources, like food or shelter, during different seasons, originating spillover movements between different environments.
2. The present study aimed to evaluate the response of the Coleoptera community to the landscape surrounding vineyards at different buffers. For that, Coleoptera were sampled in six wine protected designation of origin (PDO) regions of Portugal (35 vineyards), and landscape configuration and composition metrics were calculated at buffers of 500, 750, 1000, 1500 and 2000 m radii around the vineyards.
3. In total, 2954 Coleoptera individuals belonging to 36 families were collected. The most abundant families were Chrysomelidae, Coccinellidae and Latridiidae. Results indicated that intermediate habitat fragmentation levels, particularly in semi-natural areas and vineyards, favoured Coleoptera biodiversity in vine-producing regions. Moreover, the range of activity of Coleoptera seems to be larger than 1000 m.
4. This work constitutes an important contribution to understanding the response of the Coleoptera community to the landscape context in vineyards in Portugal and contributes to the theoretical framework about the influence of habitat fragmentation on biodiversity.

     

Characterization of Biocontrol Traits in Heterorhabditis floridensis: A Species with Broad Temperature Tolerance

Biological characteristics of two strains of the entomopathogenic nematode, Heterorhabditis floridensis (332 isolated in Florida and K22 isolated in Georgia) were described. The identity of the nematode’s symbiotic bacteria was elucidated and found to be Photorhabdus luminescens subsp. luminescens. Beneficial traits pertinent to biocontrol (environmental tolerance and virulence) were characterized. The range of temperature tolerance in the H. floridensis strains was broad and showed a high level of heat tolerance. The H. floridensis strains caused higher mortality or infection in G. mellonella at 30°C and 35°C compared with S. riobrave (355), a strain widely known to be heat tolerant, and the H. floridensis strains were also capable of infecting at 17°C whereas S. riobrave (355) was not. However, at higher temperatures (37°C and 39°C), though H. floridensis readily infected G. mellonella, S. riobrave strains caused higher levels of mortality. Desiccation tolerance in H. floridensis was similar to Heterorhabditis indica (Hom1) and S. riobrave (355) and superior to S. feltiae (SN). H. bacteriophora (Oswego) and S. carpocapsae (All) exhibited higher desiccation tolerance than the H. floridensis strains. The virulence of H. floridensis to four insect pests (Aethina tumida, Conotrachelus nenuphar, Diaprepes abbreviatus, and Tenebrio molitor) was determined relative to seven other nematodes: H. bacteriophora (Oswego), H. indica (Hom1), S. carpocapsae (All), S. feltiae (SN), S. glaseri (4-8 and Vs strains), and S. riobrave (355). Virulence to A. tumida was similar among the H. floridensis strains and other nematodes except S. glaseri (Vs), S. feltiae, and S. riobrave failed to cause higher mortality than the control. Only H. bacteriophora, H. indica, S. feltiae, S. riobrave, and S. glaseri (4-8) caused higher mortality than the control in C. nenuphar. All nematodes were pathogenic to D. abbreviatus though S. glaseri (4-8) and S. riobrave (355) were the most virulent. S. carpocapsae was the most virulent to T. molitor. In summary, the H. floridensis strains possess a wide niche breadth in temperature tolerance and have virulence and desiccation levels that are similar to a number of other entomopathogenic nematodes. The strains may be useful for biocontrol purposes in environments where temperature extremes occur within short durations.     

Laboratory method for testing side-effects of pesticides on the rove beetleAleochara bilineata — Adults

Tests were conducted in glass cells containing moistened sand sprayed with the concentration recommended for the pesticide or with demineralised water (controls). Adult females (1–2 weeks old) ofA. bilineata were placed on the fresh residue in the cells and provided daily with fresh fly eggs as food. The duration of the test was 5 days, mortality being recorded every day. The side effects of the pesticide were expressed as reduction in egg production ofA. bilineata during the whole test period. Results permitted classification of the pesticides according to the 4 categories of harmfulness used by the IOBC working group. 23 pesticides were tested, and the reproducibility of the test appeared to be satisfactory. Generally, insecticides/acaricides had a pronounced effect on the beetles whereas fungicides and herbicides were less detrimental. Exceptions were the insecticides Tedion V 18 and Kilval, classified as harmless, and the fungicides Morestan, Pomarsol forte and Afugan rated as moderately harmful. Among growth regulators Prosevor 85 was highly detrimental while Cycocel Extra and Rhodofix had no effects. Excepting Morestan, Pomarsol forte and Ustinex PA the pesticides did not affect the hatching of eggs. The work was financed by the Danish Environmental Protection Agency.     

Effects of 37 fungicides on the rove beetleAleochara bilineata (Col.: Staphylinidae) in the laboratory

Effects of 37 fungicides — several of which were mixtures — on adult females of the rove beetle,Aleochara bilineata, were investigated in the laboratory. The pesticides were tested in concentrations equivalent to the highest recommended dosages for practical use. Mortality, egg production and hatch of the eggs were recorded. Most fungicides had no serious effect on any of the parameters measured. Among the morpholine and dithiocarbamate fungicides, several had adverse effects on egg production and/or hatch of the eggs laid. Furthermore, chinomethionate and pyrazophos were found to be toxic at the dosages used. Results are compared to results obtained with other species of beneficial arthropods in the laboratory. The importance of including several species in the assessment of pesticide side effects as well as the importance of measuring sublethal effects are stressed.

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Résumé Des expériences de laboratoire ont été faites pour étudier les effets de 37 fongicides (dont plusieurs étaient des mélanges) sur les femelles adultes d'Aleochara bilineata. Les pesticides ont été testés à des concentrations équivalant aux plus fortes doses recommandées pour l'usage agricole. La mortalité, la production et l'éclosion des œufs ont été étudiées. La plupart des fongicides n'ont pas d'effet important sur aucun des paramètres retenus. Parmi les fongicides à base de morpholine et de dithiocarbamate, plusieurs avaient un effet contraire sur la production et l'éclosion des œufs. En outre le chinométhionate et le pyrazophos se sont révélés toxiques aux doses utilisées. Les résultats ont été comparés à d'autres résultats obtenus avec d'autres espèces d'auxiliaires au laboratoire. L'importance d'inclure plusieurs espèces dans l'évaluation des effects secondaires des pestieides ainsi que l'importance de mesurer les effets sublétaux sont soulignées.

     

Linking temperature dependence of fitness effects of mutations to thermal niche adaptation

Fitness effects of mutations may generally depend on temperature that influences all rate-limiting biophysical and biochemical processes. Earlier studies suggested that high temperatures may increase the availability of beneficial mutations (‘more beneficial mutations’), or allow beneficial mutations to show stronger fitness effects (‘stronger beneficial mutation effects’). The ‘more beneficial mutations’ scenario would inevitably be associated with increased proportion of conditionally beneficial mutations at higher temperatures. This in turn predicts that populations in warm environments show faster evolutionary adaptation but suffer fitness loss when faced with cold conditions, and those evolving in cold environments become thermal-niche generalists (‘hotter is narrower’). Under the ‘stronger beneficial mutation effects’ scenario, populations evolving in warm environments would show faster adaptation without fitness costs in cold environments, leading to a ‘hotter is (universally) better’ pattern in thermal niche adaptation. We tested predictions of the two competing hypotheses using an experimental evolution study in which populations of two model bacterial species, Escherichia coli and Pseudomonas fluorescens, evolved for 2400 generations at three experimental temperatures. Results of reciprocal transplant experiments with our P. fluorescens populations were largely consistent with the ‘hotter is narrower’ prediction. Results from the E. coli populations clearly suggested stronger beneficial mutation effects at higher assay temperatures, but failed to detect faster adaptation in populations evolving in warmer experimental environments (presumably because of limitation in the supply of genetic variation). Our results suggest that the influence of temperature on mutational effects may provide insight into the patterns of thermal niche adaptation and population diversification across thermal conditions.     

Impact of Phytophthora agathidicida infection on canopy and forest floor plant nutrient concentrations and fluxes in a kauri‐dominated forest

Kauri dieback, caused by Phytophthora agathidicida, is a biotic disturbance that poses a recent threat to the survival of kauri (Agathis australis) forests in New Zealand. Previous studies have shown that throughfall and stemflow play an important role in the kauri forests’ internal nutrient cycle. However, the effects of P. agathidicida infection on canopy and forest floor nutrient fluxes in kauri forests remain unknown. Here, we measured throughfall, stemflow and forest floor water yield, nutrient (potassium, calcium, magnesium, manganese, silicon, sulfur, sodium, iron) concentrations and fluxes of ten kauri trees differing in soil P. agathidicida DNA concentration, and health status. We did not observe an effect of soil P. agathidicida DNA concentration on throughfall, stemflow, and forest floor water yield. Throughfall and forest floor nutrient concentrations and fluxes decreased (up to 50%) with increasing soil P. agathidicida DNA concentration. We found significant effects on potassium and manganese fluxes in throughfall; calcium and silicon fluxes in forest floor leachate. A decline in canopy and forest floor nutrient fluxes may result in soil nutrient imbalances, which in turn may negatively impact forest productivity and may increase the susceptibility of trees to future pathogen infection in these ecologically unique kauri forests. Given our findings and the increasing spread of Phytophthora species worldwide, research on the underlying physiological mechanisms linking dieback and plant–soil nutrient fluxes is critical.