Risks and opportunities of trophic rewilding for arthropod communities
Klink, Roel van; WallisDeVries, Michiel F. - \ 2018
Philosophical Transactions of the Royal Society B. Biological sciences 373 (2018)1761. - ISSN 0962-8436 - 8 p.
grazing - insects - invertebrates - near-natural grazing - Oostvaardersplassen - restoration
Trophic rewilding is a restoration strategy focusing on the restoration of trophic interactions to promote self-regulating, biodiverse ecosystems. It has been proposed as an alternative to traditional conservation management in abandoned or defaunated areas. Arthropods constitute the most species-rich group of eukaryotic organisms, but are rarely considered in rewilding. Here, we first present an overview of direct and indirect pathways by which large herbivores and predators affect arthropod communities. We then review the published evidence of the impacts of rewilding with large herbivores on arthropods, including grey literature. We find that systematic monitoring is rare and that a comparison with a relevant control treatment is usually lacking. Nevertheless, the available data suggest that when the important process of top-down control of large-herbivore populations is missing, arthropod diversity tends to decrease. To ensure that rewilding is supportive of biodiversity conservation, we propose that if natural processes can only partially be restored, substitutes for missing processes are applied. We also propose that boundaries of acceptable outcomes of rewilding actions should be defined a priori, particularly concerning biodiversity conservation, and that action is taken when these boundaries are transgressed. To evaluate the success of rewilding for biodiversity, monitoring of arthropod communities should be a key instrument.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.
Bioaccumulation of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and hexachlorobenzene by three Arctic benthic species from Kongsfjorden (Svalbard, Norway)
Szczybelski, Ariadna S. ; Heuvel-Greve, M.J. van den; Kampen, T. ; Wang, Chenwen ; Brink, Nico van den; Koelmans, A.A. - \ 2016
Marine Pollution Bulletin 112 (2016)1-2. - ISSN 0025-326X - p. 65 - 74.
Arctic - benthos - bioindicators - BSAFs - invertebrates - POPs
The predicted expansion of oil and gas (O&G) activities in the Arctic urges for a better understanding of impacts of these activities in this region. Here we investigated the influence of location, feeding strategy and animal size on the bioaccumulation of Polycyclic Aromatic Hydrocarbons (PAHs), Polychlorinated Biphenyls (PCBs) and Hexachlorobenzene (HCB) by three Arctic benthic species in Kongsfjorden (Svalbard, Norway). No toxicity was expected based on biota PAH critical body residues. Biota PCB levels were mainly below limit of detection, whereas samples were moderately polluted by HCB. PAH concentrations in biota and Biota Sediment Accumulation Factors (BSAFs) were generally higher in Blomstrandhalvøya than in Ny-Ålesund, which was explained by a higher abundance of black carbon in Ny-Ålesund harbour. BSAFs differed significantly among species and stations. We conclude that contaminant body residues are a less variable and more straightforward monitoring parameter than sediment concentrations or BSAFs in Arctic benthos.
Intertidal biofilm distribution underpins differential tide-following behavior of two sandpiper species (Calidris mauri and Calidris alpina) during northward migration
Jimenez, A. ; Elner, R.W. ; Favaro, C. ; Rickards, K. ; Ydenberg, R.C. - \ 2015
Estuarine Coastal and Shelf Science 155 (2015). - ISSN 0272-7714 - p. 8 - 16.
fraser-river estuary - western sandpipers - shorebird distribution - sediment - waders - microphytobenthos - invertebrates - predation - abundance - cycle
The discovery that some shorebird species graze heavily on biofilm adds importance to elucidating coastal processes controlling biofilm, as well as impetus to better understand patterns of shorebird use of intertidal flats. Western sandpipers (Calidris mauri) and dunlin (Calidris alpina) stopover in the hundreds of thousands on the Fraser River estuary, British Columbia, Canada, during northward migration to breeding areas. Western sandpipers show greater modification of tongue and bill morphology for biofilm feeding than dunlin, and their diet includes more biofilm. Therefore, we hypothesized that these congeners differentially use the intertidal area. A tide following index (TFI) was used to describe their distributions in the upper intertidal during ebbing tides. Also, we assessed sediment grain size, biofilm (= microphytobenthic or MPB) biomass and invertebrate abundance. Foraging dunlin closely followed the ebbing tide line, exploiting the upper intertidal only as the tide retreated through this area. In contrast, western sandpipers were less prone to follow the tide, and spent more time in the upper intertidal. Microphytobenthic biomass and sediment water content were highest in the upper intertidal, indicating greater biofilm availability for shorebirds in the first 350 m from shore. Invertebrate density did not differ between sections of the upper intertidal. Overall, western sandpiper behaviour and distribution more closely matched MPB biofilm availability than invertebrate availability. Conservation of sandpipers should consider physical processes, such as tides and currents, which maintain the availability of biofilm, a critical food source during global migration.
Gunstige referentiewaarden voor populatieomvang en verspreidingsgebied van soorten van bijlage II, IV en V van de Habitatrichtlijn
Ottburg, F.G.W.A. ; Swaay, C.A.M. van - \ 2014
Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu, Wageningen UR (WOt-rapport 124)
amphibia - lepidoptera - vissen - zoogdieren - ongewervelde dieren - mossen - korstmossen - reptielen - populatiebiologie - habitatrichtlijn - amphibia - lepidoptera - fishes - mammals - invertebrates - mosses - lichens - reptiles - population biology - habitats directive
This report presents the Favourable Reference Values for population size and range for the species listed in Annexes II, IV and V of the EU Habitats Directive. These reference values are used to assess the conservation status of species as required by Article 17 of the Habitats Directive. They were determined according to a protocol (checklist) and based on scientific information. Where the required scientific information was not readily available, expert judgement was used to fill the gaps. When determining the reference values, experts on each of the species groups were enlisted from the various voluntary conservation organisations, IMARES Wageningen UR (Texel and IJmuiden) and Alterra Wageningen UR. In addition, two extra questions were answered on how these reference values can be maintained or achieved, and the potential influence of climate warming.
The need for attuned soil quality risk assessment for non-Western humans and ecosystems, exemplified by mining areas in South Africa
Eijsackers, H.J.P. ; Swartjes, F.A. ; Rensburg, L. van; Maboeta, M.S. - \ 2014
Environmental Science & Policy 44 (2014). - ISSN 1462-9011 - p. 174 - 180.
tailings disposal facilities - heavy-metal pollution - eisenia-foetida - aporrectodea-caliginosa - chemical-properties - platinum mine - netherlands - geophagy - invertebrates - management
Worldwide, soils are under threat of deterioration and contamination due to anthropogenic activities. Whilst risk assessment of soils in Europe has been well studied, the same cannot be said of soils in Southern Africa. Soil screening values exist in SA, which enables soil quality assessment, but lack a clear risk-based scientific foundation and site-specific risk assessment. This is specified, in the light of the proximity of mine tailings disposal facilities to residential areas, exposing people to a wide range of possible contaminants. The aim of this paper is to give an overview of soil quality risk assessment with specific reference to European models, and to explore how these could be used in a Southern African context where soil quality risk assessment is a relatively new and insufficiently investigated field. Therefore, the attention in this paper is on typical non-Western conditions to which soil quality risk assessment has to be attuned. (C) 2014 Elsevier Ltd. All rights reserved.
Le valeurs nutritionnelles des invertebrés : un aperçu du contenu nutritionnel, sur une base matière sèche, des espèces d’invertébrés utilisés comme nourriture
Huisman, T.R. ; Hokwerda, J. - \ 2014
VHL Animal Management, Animal Welfare Web (DWW)
dierentuindieren - diervoeding - dierenwelzijn - diergezondheid - voedingswaarde - ongewervelde dieren - zoo animals - animal nutrition - animal welfare - animal health - nutritive value - invertebrates
Poster met een overzicht van de voedingswaarde van invertebraten.
Chronic aquatic effect assessment for the fungicide azoxystrobin
Wijngaarden, R.P.A. van; Belgers, J.D.M. ; Zafar, M.I. ; Matser, A.M. ; Boerwinkel, M.C. ; Arts, G.H.P. - \ 2014
Environmental Toxicology and Chemistry 33 (2014)12. - ISSN 0730-7268 - p. 2775 - 2785.
fresh-water microcosms - herbicide linuron - primary producers - outdoor ponds - responses - 3,4-dichloroaniline - chlorpyrifos - sensitivity - fate - invertebrates
This study examined ecological effects of a range of chronic exposure concentrations of the fungicide azoxystrobin in freshwater experimental systems (1270 L outdoor microcosms). Intended and environmentally relevant test concentrations of azoxystrobin were 0, 0.33, 1, 3.3, 10, 33 µg ai/L, kept at constant values. Responses of freshwater populations and community parameters were studied. Over the 42-day experimental period, the time-weighted average concentrations of azoxystrobin ranged from 93.5 to 99.3% of intended values. Zooplankton, especially copepods and Daphnia group longispina, were the most sensitive groups. At the population level, a consistent NOEC of 1 µg ai/L was calculated for Copepoda. The NOEC at the zooplankton community level was 10 µg azoxystrobin/L. The principle of the EU pesticide directive is that lower-tier Regulatory Acceptable Concentrations (RACs) are protective of higher-tier RACs. This was tested for chronic risks from azoxystrobin. With the exception of the microcosm community chronic RAC (highest tier), all other chronic RAC values were similar to each other (0.5 – 1 µg ai/L). The new and stricter first-tier species requirements of the EU pesticide regulation (1107/2009/EC) are not protective for the most sensitive populations in the microcosm study, when based on the higher-tier population RAC. In comparison, the Water Framework Directive (WFD) generates Environmental Quality Standards (EQS) which are 5 - 10 times lower than the derived chronic RACs.
Effects of silver nanoparticles (NM-300K) on Lumbricus rubellus earthworms and particle characerization in relevant test matrices including soil
Ploeg, M.J.C. van der; Handy, R.D. ; Waalewijn-Kool, P. ; Berg, J.H.J. van den; Herrera Rivera, Z.E. ; Bovenschen, J. ; Molleman, B. ; Baveco, J.M. ; Tromp, P. ; Peters, R.J.B. ; Koopmans, G.F. ; Rietjens, I. ; Brink, N.W. van den - \ 2014
Environmental Toxicology and Chemistry 33 (2014)4. - ISSN 0730-7268 - p. 743 - 752.
in-vitro - size - invertebrates - oligochaeta - dissolution - responses - toxicity - exposure - behavior - impacts
The impact of silver nanoparticles (AgNP; at 0¿mg Ag/kg, 1.5¿mg Ag/kg, 15.4¿mg Ag/kg, and 154¿mg Ag/kg soil) and silver nitrate (AgNO3; 15.4¿mg Ag/kg soil) on earthworms, Lumbricus rubellus, was assessed. A 4-wk exposure to the highest AgNP treatment reduced growth and reproduction compared with the control. Silver nitrate (AgNO3) exposure also impaired reproduction, but not as much as the highest AgNP treatment. Long-term exposure to the highest AgNP treatment caused complete juvenile mortality. All AgNP treatments induced tissue pathology. Population modeling demonstrated reduced population growth rates for the AgNP and AgNO3 treatments, and no population growth at the highest AgNP treatment because of juvenile mortality. Analysis of AgNP treated soil samples revealed that single AgNP and AgNP clusters were present in the soil, and that the total Ag in soil porewater remained high throughout the long-term experiment. In addition, immune cells (coelomocytes) of earthworms showed sensitivity to both AgNP and AgNO3 in vitro. Overall, the present study indicates that AgNP exposure may affect earthworm populations and that the exposure may be prolonged because of the release of a dissolved Ag fraction to soil porewater.
Ethoprophos fate on soil-water interface and effects on non-target terrestrial and aquatic biota under Mediterranean crop-based scenarios
Leitao, S. ; Moreira-Santos, M. ; Brink, P.J. van den; Ribeiro, R. ; Cerejeira, J. ; Sousa, J.P. - \ 2014
Ecotoxicology and Environmental Safety 103 (2014). - ISSN 0147-6513 - p. 36 - 44.
species sensitivity distributions - fungicide azoxystrobin - folsomia-candida - sandy soil - pesticides - toxicity - invertebrates - earthworms - bentazone - transport
The present study aimed to assess the environmental fate of the insecticide and nematicide ethoprophos in the soil-water interface following the pesticide application in simulated maize and potato crops under Mediterranean agricultural conditions, particularly of irrigation. Focus was given to the soil-water transfer pathways (leaching and runoff), to the pesticide transport in soil between pesticide application (crop row) and non-application areas (between crop rows), as well as to toxic effects of the various matrices on terrestrial and aquatic biota. A semi-field methodology mimicking a "worst-case" ethoprophos application (twice the recommended dosage for maize and potato crops: 100% concentration v/v) in agricultural field situations was used, in order to mimic a possible misuse by the farmer under realistic conditions. A rainfall was simulated under a slope of 20° for both crop-based scenarios. Soil and water samples were collected for the analysis of pesticide residues. Ecotoxicity of soil and aquatic samples was assessed by performing lethal and sublethal bioassays with organisms from different trophic levels: the collembolan Folsomia candida, the earthworm Eisenia andrei and the cladoceran Daphnia magna. Although the majority of ethoprophos sorbed to the soil application area, pesticide concentrations were detected in all water matrices illustrating pesticide transfer pathways of water contamination between environmental compartments. Leaching to groundwater proved to be an important transfer pathway of ethoprophos under both crop-based scenarios, as it resulted in high pesticide concentration in leachates from Maize (130µgL(-1)) and Potato (630µgL(-1)) crop scenarios, respectively. Ethoprophos application at the Potato crop scenario caused more toxic effects on terrestrial and aquatic biota than at the Maize scenario at the recommended dosage and lower concentrations. In both crop-based scenarios, ethoprophos moved with the irrigation water flow to the soil between the crop rows where no pesticide was applied, causing toxic effects on terrestrial organisms. The two simulated agricultural crop-based scenarios had the merit to illustrate the importance of transfer pathways of pesticides from soil to groundwater through leaching and from crop rows to the surrounding soil areas in a soil-water interface environment, which is representative for irrigated agricultural crops under Mediterranean conditions.
Integrating chemical fate and population-level effect models of pesticides: the importance of capturing the right scales
Focks, A. ; Horst, M.M.S. ter; Berg, E. van den; Baveco, H. ; Brink, P.J. van den - \ 2014
Ecological Modelling 280 (2014). - ISSN 0304-3800 - p. 102 - 116.
asellus-aquaticus l - potential application - lambda-cyhalothrin - life-history - growth - invertebrates - isopoda - field - ecotoxicology - biodiversity
Any attempt to introduce more ecological realism into ecological risk assessment of chemicals faces the major challenge of integrating different aspects of the chemicals and species of concern, for example, spatial scales of emissions, chemical exposure patterns in space and time, and population dynamics and dispersal in heterogeneous landscapes. Although these aspects are not considered in current risk assessment schemes, risk assessors and managers are expressing increasing interest in learning more about both the exposure to and the effects of chemicals at landscape level. In this study, we combined the CASCADE-TOXSWA fate model, which predicts the fate of pesticides in an interconnected system of water bodies with variable hydrological characteristics, with the MASTEP mechanistic effect model, which simulates population dynamics and effects of pesticides on aquatic species at the scale of individual water bodies. To this end, we extrapolated MASTEP to the scale of realistic landscapes and linked it to dynamic exposure patterns. We explored the effects of an insecticide on the water louse Asellus aquaticus for a typical Dutch landscape covering an area of about 10 km2 containing 137 water bodies (drainage ditches) with a total length of about 65 km and different degrees of connectivity. Pesticide treatments used in potato crop were assumed to result in a spray-drift input of 5% (non-mitigated) and 1% (mitigated) of the amount of pesticide applied into parts of the water body network. These treatments resulted in highly variable exposure patterns both in space and time. The effects of the pesticide on the species were investigated by comparing two scenarios with low and high individual-level sensitivity. We found that downstream transport of the pesticide led to exposure of water bodies that did not receive direct spray-drift input, even though this particular pesticide was assumed to dissipate rapidly from water. The observed differences in population-level effects and recovery patterns ranged from no observable effects in the low spray-drift and low sensitivity scenario to severe reduction of abundances in the high spray-drift and high sensitivity scenario. These results illustrate the sensitivity of our modelling approach, but also show the need for precise calculations of pesticide inputs and model parameterisation. Our study demonstrates the potential of coupled fate-and-effect to explore realistic scenarios at the scale of heterogeneous landscapes. Such scenarios could include the application of multiple pesticides to one or more crop types. Spatial realism of the landscape represented in the model ensures realistic consideration of population growth and dispersal as the two main recovery mechanisms. Future options for the landscape-scale fate-and-effect simulation approach include exploring the effects of mitigation measures on the risk estimates at landscape scale and hence represent a step towards risk management.
Insect lipid profile: aqueous versus organic solvent-based extraction methods
Tzompa Sosa, D.A. ; Yi, L. ; Valenberg, H.J.F. van; Boekel, M.A.J.S. van; Lakemond, C.M.M. - \ 2014
Food Research International 62 (2014). - ISSN 0963-9969 - p. 1087 - 1094.
edible insects - fatty-acids - nutrient composition - food - invertebrates - meat - seed - oils
In view of future expected industrial bio-fractionation of insects, we investigated the influence of extraction methods on chemical characteristics of insect lipids. Lipids from Tenebrio molitor, Alphitobius diaperinus, Acheta domesticus and Blaptica dubia, reared in the Netherlands, were extracted by two industrial extraction processes (aqueous and Soxhlet) and one laboratory method (Folch extraction). Chemical characterization in terms of fatty acid composition (GC-FID), triacylglycerol profile (GC) and lipid classes (TLC) was performed on all the extracted lipids. The major findings on lipid chemical characterization were the following: (1) T. molitor had the highest lipid content around 13%; (2) the highest yield was obtained using Folch extraction, and the lowest yield using the aqueous method (from 19 to 60% related to the lipid recovery of Folch extraction); (3) ¿-3 fatty acids,which are related to health benefits, weremost abundant in lipids fromaqueous extraction,while¿-6 fatty acids were most abundant in Folch extractions, except for B. dubia; (4) lipids from Folch and Soxhlet extractions contained free fatty acids and partial glycerides, which were absent in aqueous extractions; (5) triacylglycerol distribution is similar among insect species, with high levels of ECN 50–54 and low amounts of ECN 36–38. In conclusion, aqueous extraction gave the lowest lipid yield, but provided a lipid extract low in ¿-6/¿-3 ratio and with less polar lipids than Soxhlet and Folch extractions. These characteristics are desirable in edible lipids. This is the first time that the triacylglycerol profile of insect lipids is reported. It is also the first time that C18:1 and C18:2 are reported as separated isomers and that trans isomers of C16:1 and C18:1 are reported in insect lipids.
Impact on demersal fish of a large-scale and deep sand extraction site with ecosystem-based landscaped sandbars
Jong, M.F. de; Baptist, M.J. ; Hal, R. van; Boois, I.J. de; Lindeboom, H.J. ; Hoekstra, P. - \ 2014
Estuarine Coastal and Shelf Science 146 (2014). - ISSN 0272-7714 - p. 83 - 94.
southern north-sea - pleuronectes-platessa - limanda-limanda - marine sand - plaice - invertebrates - assemblages - environment - responses - habitats
For the seaward harbour extension of the Port of Rotterdam in the Netherlands, approximately 220 million m3 sand was extracted between 2009 and 2013. In order to decrease the surface area of direct impact, the authorities permitted deep sand extraction, down to 20 m below the seabed. Biological and physical impacts of large-scale and deep sand extraction are still being investigated and largely unknown. For this reason, we investigated the colonization of demersal fish in a deep sand extraction site. Significant differences in demersal fish species assemblages in the sand extraction site were associated with variables such as water depth, median grain size, fraction of very fine sand, biomass of white furrow shell (Abra alba) and time after the cessation of sand extraction. Large quantities of undigested crushed white furrow shell fragments were found in all stomachs and intestines of plaice (Pleuronectes platessa), indicating that it is an important prey item. One and two years after cessation, a significant 20-fold increase in demersal fish biomass was observed in deep parts of the extraction site. In the troughs of a landscaped sandbar however, a significant drop in biomass down to reference levels and a significant change in species assemblage was observed two years after cessation. The fish assemblage at the crests of the sandbars differed significantly from the troughs with tub gurnard (Chelidonichthys lucerna) being a Dufrêne-Legendre indicator species of the crests. This is a first indication of the applicability of landscaping techniques to induce heterogeneity of the seabed although it remains difficult to draw a strong conclusion due the lack of replication in the experiment. A new ecological equilibrium is not reached after 2 years since biotic and abiotic variables are still adapting. To understand the final impact of deep and large-scale sand extraction on demersal fish, we recommend monitoring for a longer period, at least for a period of six years or even longer. Keywords infauna; epifauna; sediment; ground fish; sand mining; North Sea
Land-Use and Land-Management Change: Relationships with Earthworm and Fungi Communities and Soil Structural Properties
Spurgeon, D.J. ; Keith, A.M. ; Schmidt, O. ; Lammertsma, D.R. ; Faber, J.H. - \ 2013
BMC Ecology 13 (2013). - ISSN 1472-6785 - 13 p.
arbuscular mycorrhizal fungi - ectomycorrhizal fungi - aggregate stability - ecosystem services - organic-matter - common garden - no-till - biodiversity - europe - invertebrates
Background Change in land use and management can impact massively on soil ecosystems. Ecosystem engineers and other functional biodiversity in soils can be influenced directly by such change and this in turn can affect key soil functions. Here, we employ meta-analysis to provide a quantitative assessment of the effects of changes in land use and land management across a range of successional/extensification transitions (conventional arable¿¿¿no or reduced tillage¿¿¿grassland¿¿¿wooded land) on community metrics for two functionally important soil taxa, earthworms and fungi. An analysis of the relationships between community change and soil structural properties was also included. Results Meta-analysis highlighted a consistent trend of increased earthworm and fungal community abundances and complexity following transitions to lower intensity and later successional land uses. The greatest changes were seen for early stage transitions, such as introduction of reduced tillage regimes and conversion to grassland from arable land. Not all changes, however, result in positive effects on the assessed community metrics. For example, whether woodland conversion positively or negatively affects community size and complexity depends on woodland type and, potentially, the changes in soil properties, such as pH, that may occur during conversion. Alterations in soil communities tended to facilitate subsequent changes in soil structure and hydrology. For example, increasing earthworm abundances and functional group composition were shown to be positively correlated with water infiltration rate (dependent on tillage regime and habitat characteristics); while positive changes in fungal biomass measures were positively associated with soil microaggregate stability. Conclusions These findings raise the potential to manage landscapes to increase ecosystem service provision from soil biota in relation to regulation of soil structure and water flow. Keywords: Meta analysis; Earthworm; Fungi; Functional biodiversity; Soil porosity; Microaggregate stability
Aandacht voor ongewervelden in het natuurbeleid
Wallis de Vries, M.F. - \ 2013
De Levende Natuur 114 (2013)5. - ISSN 0024-1520 - p. 167 - 170.
lepidoptera - ongewervelde dieren - fauna - natuurbeheer - lepidoptera - invertebrates - fauna - nature management
In het natuurbeleid is er al lange tijd veel aandacht voor de gewervelde fauna. Om praktische redenen van doelmatigheid en beschikbare kennis over verspreiding en ecologie lijkt dat terecht, maar er zijn goede redenen voor een prominentere plaats voor ongewervelden. Ook op basis van de soortenrijkdom zou je veel meer aandacht voor ongewervelde dieren mogen verwachten. De vraag is wel hoe die moet worden ingevuld. In het kort worden hier de positie en de waarde van ongewervelden in het natuurbeleid uiteen gezet.
The use of statistical tools in field testing of putative effects of genetically modified plants on nontarget organisms
Semenov, A.V. ; Elsas, J.D. van; Glandorf, D.C.M. ; Schilthuizen, M. ; Boer, W.F. de - \ 2013
Ecology and Evolution 3 (2013)8. - ISSN 2045-7758 - p. 2739 - 2750.
herbicide-tolerant crops - farm-scale evaluations - gene flow - population-structure - habitat preference - land snail - dispersal - design - power - invertebrates
To fulfill existing guidelines, applicants that aim to place their genetically modified (GM) insect-resistant crop plants on the market are required to provide data from field experiments that address the potential impacts of the GM plants on nontarget organisms (NTO's). Such data may be based on varied experimental designs. The recent EFSA guidance document for environmental risk assessment (2010) does not provide clear and structured suggestions that address the statistics of field trials on effects on NTO's. This review examines existing practices in GM plant field testing such as the way of randomization, replication, and pseudoreplication. Emphasis is placed on the importance of design features used for the field trials in which effects on NTO's are assessed. The importance of statistical power and the positive and negative aspects of various statistical models are discussed. Equivalence and difference testing are compared, and the importance of checking the distribution of experimental data is stressed to decide on the selection of the proper statistical model. While for continuous data (e.g., pH and temperature) classical statistical approaches - for example, analysis of variance (ANOVA) - are appropriate, for discontinuous data (counts) only generalized linear models (GLM) are shown to be efficient. There is no golden rule as to which statistical test is the most appropriate for any experimental situation. In particular, in experiments in which block designs are used and covariates play a role GLMs should be used. Generic advice is offered that will help in both the setting up of field testing and the interpretation and data analysis of the data obtained in this testing. The combination of decision trees and a checklist for field trials, which are provided, will help in the interpretation of the statistical analyses of field trials and to assess whether such analyses were correctly applied.
Multitrophic interactions on a range-expanding plant species
Fortuna, T.F.M. - \ 2013
Wageningen University. Promotor(en): Louise Vet; J.A. Harvey. - Wageningen : Wageningen UR - ISBN 9789461737656 - 229
planten - invasieve soorten - geïntroduceerde soorten - herbivoren - ongewervelde dieren - natuurlijke vijanden - predatoren - parasitoïden - multitrofe interacties - bunias orientalis - verdedigingsmechanismen - plants - invasive species - introduced species - herbivores - invertebrates - natural enemies - predators - parasitoids - multitrophic interactions - bunias orientalis - defence mechanisms
Studies on the ecological impacts of exotic invasive plants have mainly focused on inter-continental invasions. However due to global environmental changes, a rapid increase in intra-continental range-expanding plants has been observed. In this context, multitrophic interactions between exotic plants, native herbivores and their natural enemies have been largely ignored. This thesis aimed at examining how an exotic range-expanding plant interacts with aboveground insect herbivores and their natural enemies and how it can contribute to the successful establishment of the exotic plant. In addition, it examines how resistance traits of different populations of the range-expander affect the behaviour and performance of herbivores and their natural enemies in the new habitat. Bunias orientalis (Capparales: Brassicaceae) is perennial plant from extreme south-eastern Europe and Asia that has recently expanded its range and become invasive in northern and central parts of Europe. In the Netherlands, it is considered naturalized but non-invasive.
Firstly, using a community approach, I found that Bu. orientalis suffered less herbivore damage and harboured smaller invertebrate communities than sympatric native Brassicaceae in the Netherlands. The exotic plant has been found of low quality for the larval growth of the specialist herbivore (Pieris brassicae). Furthermore, two of its gregarious parasitoids were differentially affected by the quality of the exotic plant. The pupal parasitoid (Pteromalus puparum) survived better than the larval parasitoid (Cotesia glomerata), and the latter parasitized less hosts on the exotic than on native plants. Therefore, the herbivore can be selected to adapt to the new plant by conferring an enemy free space to the herbivore. In this case, a plant shift by the specialist herbivore might occur and thus preventing the further spread of the exotic plant. Conversely, in the field I found greater carnivore pressure on Bu. orientalis compared to other native Brassicaceae, particularly in the peak of arthropod abundance. Hence, top-down forces exerted by herbivore natural enemies may act in concert with bottom-up control of plant resistance traits to counteract herbivore plant shift and promote the successful range expansion of the exotic plant.
Secondly, using a biogeographical approach, I found a considerable intraspecific variation in defence traits (trichomes, glucosinolates, metabolic fingerprints) of Bu. orientalis populations from the native and the exotic range. Plants collected in the native range were better defended than their exotic conspecifics. This variation matched with the performance of a generalist herbivore (Mamestra brassicae) and its parasitoid (Microplitis mediator), which developed poorly in plants from the native range. The results suggest that the defensive mechanisms of Bu. orientalis might have been counter-selected during the range expansion of the exotic plant. Further studies, however, need to examine if enemy release in the new range is followed by an increase in performance of the exotic plant. Finally, a comparative study of multitrophic interactions, both above- and belowground, in the plant native range and along the transect of its range expansion can help to clarify the mechanisms underlying the invasive success of Bu. orientalis.
Sediment macroinvertebrate community functioning in impacted and newly-created tidal freshwater habitats
Beauchard, O. ; Jacobs, S. ; Ysebaert, T. ; Meire, P. - \ 2013
Estuarine Coastal and Shelf Science 120 (2013). - ISSN 0272-7714 - p. 21 - 32.
terrestrial food webs - co-inertia analysis - environment relationships - ecosystem function - 4th-corner problem - real differences - schelde estuary - species traits - invertebrates - ecology
Although experiencing strong anthropogenic pressures in many estuaries, the ecology of tidal freshwater areas remains largely undocumented. As part of a restoration project in the freshwater zone of the Schelde estuary (Belgium), a new tidal habitat restoration technique (Controlled Reduced Tide system, CRT) was hypothesised to successfully compensate for the impairment of contemporary habitats. The suitability of this newly-created habitat (CRT) and the estuary was investigated over a period of three years for its macroinvertebrate community development. In both the estuary and the CRT, habitats along a flooding gradient were monitored. Differences between the CRT and reference sites in community functioning were explored according to environmental characteristics and organism biological attributes using the RLQ ordination analysis together with the fourth-corner method. Frequently flooded reference sites exhibited environmental characteristics resulting from a hydrological shear stress. In the CRT, after a rapid removal of the terrestrial fauna at low and mid elevations, the low-energy hydrology led to taxonomic and functional enrichment. The RLQ analysis produced significant environmental filtering of biological attributes mainly related to the terrestrial–aquatic transition and to the environmental stressors. This provides an example of life history modification via estuarine ecosystem management.
Koolstofnanodeeltjes hebben invloed op samenstelling waterleven
Velzeboer, I. - \ 2013
Nature Today (2013).
waterorganismen - ongewervelde dieren - fauna - nanotechnologie - nadelige gevolgen - aquatic organisms - invertebrates - fauna - nanotechnology - adverse effects
Koolstofnanodeeltjes blijken op lange termijn al bij lage concentraties effecten te hebben op het leven in het oppervlaktewater. Uit een proef onder natuurlijke veldomstandigheden komt naar voren dat de soortensamenstelling van ongewervelde waterdieren veranderde na langdurige blootstelling aan deze minuscule deeltjes. Het onderzoek is gedaan door Ilona Velzeboer van Wageningen University en onderzoeksinstituut IMARES van Wageningen UR. Zij publiceerde haar onderzoek in het toonaangevende tijdschrift Environmental Science & Technology.
Extraction and characterisation of protein fractions from five insect species
Yi, L. ; Lakemond, C.M.M. ; Sagis, L.M.C. ; Eisner-Schadler, V.R. ; Huis, A. van; Boekel, M.A.J.S. van - \ 2013
Food Chemistry 141 (2013)4. - ISSN 0308-8146 - p. 3341 - 3348.
tenebrio-molitor larvae - nutrient composition - gel formation - midgut - food - invertebrates - phenoloxidase - coleoptera - component - melanin
Tenebrio molitor, Zophobas morio, Alphitobius diaperinus, Acheta domesticus and Blaptica dubia were evaluated for their potential as a future protein source. Crude protein content ranged from 19% to 22% (Dumas analysis). Essential amino acid levels in all insect species were comparable with soybean proteins, but lower than for casein. After aqueous extraction, next to a fat fraction, a supernatant, pellet, and residue were obtained, containing 17–23%, 33–39%, 31–47% of total protein, respectively. At 3% (w/v), supernatant fractions did not form stable foams and gels at pH 3, 5, 7, and 10, except for gelation for A. domesticus at pH 7. At 30% w/v, gels at pH 7 and pH 10 were formed, but not at pH 3 and pH 5. In conclusion, the insect species studied have potential to be used in foods due to: (1) absolute protein levels; (2) protein quality; (3) ability to form gels.
Field margins as foraging habitat for skylarks (Alauda arvensis) in the breeding season
Kuiper, M.W. ; Ottens, H.J. ; Cenin, L. ; Schaffers, A.P. ; Ruijven, J. van; Koks, B.J. ; Berendse, F. ; Snoo, G.R. de - \ 2013
Agriculture, Ecosystems and Environment 170 (2013). - ISSN 0167-8809 - p. 10 - 15.
agri-environment schemes - farmland birds - agricultural intensification - food resources - ecological effectiveness - population trends - landscape context - biodiversity - management - invertebrates
Agri-environment schemes have been established in many European countries to counteract the ongoing decline of farmland birds. In this study, the selection of foraging habitat by breeding skylarks was examined in relation to agri-environmental management on Dutch farmland. Field margin use was quantified and, based on the observed flight distances, the appropriateness of the current spatial arrangement of field margins in the study landscape was evaluated. Skylarks preferred field margins for foraging over all other habitat types relative to their surface area within the territories. The visiting rate of field margins decreased with increasing distance to the nest, and especially dropped markedly when the distance between the nest and a field margin exceeded 100 m. Analysis of the current spatial arrangement of field margins in the landscape suggested that the area of skylark breeding habitat within 100 m of a field margin could be increased by 46%. This was due to the placement of field margins alongside unsuitable breeding habitat and to the positioning of field margins at short distances from each other. The efficiency of agri-environmental management for skylarks can likely be improved by a more careful spatial arrangement of field margins in the landscape.