Natural variation in virulence of the entomopathogenic fungus Beauveria bassiana against malaria mosquitoes
Valero Jimenez, C.A. ; Debets, A.J.M. ; Kan, J.A. van; Schoustra, S.E. ; Takken, W. ; Zwaan, B.J. ; Koenraadt, C.J.M. - \ 2014
Malaria Journal 13 (2014). - ISSN 1475-2875 - 8 p.
metarhizium-anisopliae - anopheles-gambiae - infection - agents - susceptibility - degradation - persistence - expression - resistance - behavior
Background Insecticide resistance is greatly hampering current efforts to control malaria and therefore alternative methods are needed. Entomopathogenic fungi have been proposed as an alternative with a special focus on the cosmopolitan species Beauveria bassiana. However, few studies have analysed the effects of natural variation within fungal isolates on mosquito survival, and the implications and possible exploitation for malaria control. Methods Laboratory bioassays were performed on adult female mosquitoes (Anopheles coluzzii) with spores from 29 isolates of B. bassiana, originating from different parts of the world. In addition, phenotypic characteristics of the fungal isolates such as sporulation, spore size and growth rate were studied to explore their relationship with virulence. Results All tested isolates of B. bassiana killed An. coluzzii mosquitoes, and the rate at which this happened differed significantly among the isolates. The risk of mosquitoes dying was around ten times higher when they were exposed to the most virulent as compared to the least virulent isolate. There was significant variation among isolates in spore size, growth rate and sporulation, but none of these morphological characteristics were correlated, and thus predictive, for the ability of the fungal isolate to kill malaria mosquitoes. Conclusions This study shows that there is a wide natural variation in virulence of isolates of B. bassiana, and that selecting an appropriate fungal isolate is highly relevant in killing and thus controlling malaria mosquitoes, particularly if used as part of an integrated vector management strategy. Also, the wide variation observed in virulence offers the opportunity to better understand the molecular and genetic mechanisms that drive this variation and thus to address the potential development of resistance against entomopathogenic fungi
Modelling population dynamics of the Common hamster (Cricetus cricetus): Timing of harvest as a critical aspect in the conservation of a highly endangered rodent
Haye, M.J.J. la; Swinnen, K.R.R. ; Kuiters, A.T. ; Leirs, H. ; Siepel, H. - \ 2014
Biological Conservation 180 (2014). - ISSN 0006-3207 - p. 53 - 61.
farmland bird populations - agricultural intensification - persistence - calandra
The Common hamster Cricetus cricetus was an agricultural pest in large parts of Europe less than 50 years ago. Currently the species is highly threatened or locally extinct and acknowledged as an important and even iconic species for nature conservation in farmland areas in Western Europe. The species was listed in the European habitats directive in 1992 to prevent a further decline, but the Common hamster is still declining in most parts of its European range despite large conservation efforts. Only a few local conservation successes have been reported so far. These disappointing conservation results raise the question: why is it so difficult to conserve this former pest species? Farming practices have been intensified in Europe and this has resulted in a more efficient way of harvesting cereals in combination with a strong reduction of spring sown cereals in favour of winter sown cereals. It is possible that these changes have become an important threat for survival of populations of this species. We developed both a deterministic and a stochastic population model for a better understanding of the current way of harvesting on the population ecology of this species and evaluated the effects of using different litter sizes on population growth and persistence. Our results suggest that under the current efficient harvest of cereals in Europe, it is highly unlikely that females of the Common hamster produce enough offspring for a sustainable population. Conservation projects for this species should focus on creating cereal fields which are not harvested until the end of August, as lack of cover is a major cause of high predation rates.
Preferential flow as a potential mechanism for fire-induced increase in streamflow
Stoof, C.R. ; Slingerland, E.C. ; Mol, W. ; Berg, J. van den; Vermeulen, P.J. ; Ferreira, A.J.D. ; Ritsema, C.J. ; Parlange, J.Y. ; Steenhuis, T.S. - \ 2014
Water Resources Research 50 (2014)2. - ISSN 0043-1397 - p. 1840 - 1845.
soil-water repellency - portuguese shrubland - wildfire - persistence
After vegetation fires, discharge of streams and rivers is often higher than before. This is usually attributed to decreased canopy interception and evapotranspiration caused by vegetation removal, and to increased overland flow resulting from increased soil water repellency. In this paper we examine whether fire-induced changes in preferential flow can reinforce this postfire streamflow response. We studied five recently burned soils and adjacent unburned soils in Portugal and found that by reducing topsoil moisture and increasing soil moisture variability, fire increased the propensity for preferential flow. This was confirmed by 2-D soil moisture and repellency profiles that showed preferential paths in burned soil that were more distinct, wetter, and slightly narrower than in unburned soil. Since water infiltrating along preferential flow paths bypasses the dry soil matrix, we suggest that narrow flow paths promote deep infiltration– which effect size varies with soil depth, (effective) rainfall, and overland flow. We pose that the resulting increase in infiltration increases drainage and interflow because the excess water cannot stay in the soil, and incorporate fire-induced or -enhanced preferential flow into a conceptual model of flow routing that explains the commonly observed increase in stream flow postfire.
Developing the role of perennial forages for crop-livestock farms: a strategic multi-disciplinary approach
Llewellyn, R. ; Robertson, M.J. ; Hayes, R.C. ; Ferris, D. ; Descheemaeker, K.K.E. ; Revell, C. - \ 2014
Crop and Pasture Science 65 (2014)10. - ISSN 1836-0947 - p. 945 - 955.
subtropical grasses - potential scale - stocking rate - systems - pasture - australia - persistence - grain - adoption - lucerne
Developing new and improved grazing systems for crop–livestock farms where crop production is the major driver of farm management decisions presents a unique research and development challenge. In southern Australia, a substantial proportion of animal production from grazing comes from regions and farms where cropping is the major enterprise. In this paper, we describe a multi-disciplinary farming-systems research approach (EverCrop) aimed at improving farm profitability, risk management and environmental impacts through the development and integration of new grazing options with an emphasis on perennial species. It has been used to analyse and target new opportunities for farmers to benefit from perennial species across dry Mediterranean-type and temperate regions of southern Australia. It integrates field experimentation, on-farm trialling, farmer participatory research, soil–plant–climate biophysical modelling, whole-farm bioeconomic analysis and evaluations of adoptability. Multi-functional roles for summer-active grasses with winter cropping, integration of forage shrubs and establishment of new mixes of perennial grasses in crop rotations to improve farming system performance are identified, along with an analysis of factors likely to affect rate of uptake by farmers.
Pathways for resilience in Mediterranean cork oak land use systems
Acácio, V.C. ; Holmgren, M. - \ 2014
Annals of Forest Science 71 (2014)1. - ISSN 1286-4560 - p. 5 - 13.
stress-gradient hypothesis - eastern iberian peninsula - arid ecosystems - south-america - el-nino - regeneration - facilitation - restoration - persistence - landscapes
Context Loss of woodlands and degradation of vegetation and soil have been described for all Mediterranean-type ecosystems worldwide. In the Western Iberian Peninsula, overexploitation of evergreen cork oak land use systems has led to soil erosion, failures in oak recruitment, and loss of forests. Degraded and dry sites are quickly colonised by pioneer heathland rockrose (Cistus spp.) shrubs forming highly persistent patches. Aims Although traditionally shrublands have been considered as a transient successional state, we present evidence that they can represent persistent alternative states to former cork oak forests. Review trends and conclusions We first describe how Mediterranean vegetation evolved in the Iberian Peninsula and the role of fire and long-term human management as main disturbances. We then discuss alternative pathways through state-and-transition models indicating the ecological and land use variables that halt cork oak regeneration and recruitment and drive vegetation transitions towards persistent shrublands. Unless concerted management actions and restoration programmes are undertaken, the cork oak land use systems will not be sustainable
Acceptability of inversely-modelled parameters for non-equilibrium sorption of pesticides in soil
Horst, M.M.S. ter; Boesten, J.J.T.I. ; Beinum, W. van; Beulke, S. - \ 2013
Environmental Modelling & Software 46 (2013). - ISSN 1364-8152 - p. 260 - 270.
sensitivity-analysis - simulation - isoproturon - persistence - lysimeters
Simulation of the increase of sorption in time is one of the options in higher tiers of pesticide regulatory leaching assessments to obtain more realistic leaching estimates. Therefore, accurate estimates of non-equilibrium sorption parameters are required as input for the pesticide leaching scenarios. Usually, non-equilibrium sorption is described with a two-site equilibrium/non-equilibrium model in which the non-equilibrium sorption is described with two parameters (i.e. the desorption rate coefficient of the non-equilibrium site and the Freundlich sorption coefficient of this site). Estimates of these parameters can be obtained with inverse modelling techniques. At the moment, there is little understanding about whether the confidence intervals provided by inverse modelling can be used as measure of the likely accuracy (i.e. how close the estimated value is to the true value) of these estimates. We set up a semi-global inverse modelling exercise for a large number of parameter sets (Le. different pesticides) using simulated datasets. Inverse modelling of non-equilibrium parameters demonstrated decreasing accuracy of the estimates for decreasing values of the non-equilibrium sorption parameters and the equilibrium sorption coefficient. Furthermore, we found a relationship between the accuracy of a parameter estimate and its CV (coefficient of variation) provided by the inverse modelling technique. Using this relationship we calculated the likelihood of rightly or wrongly accepting or rejecting a parameter estimate as a function of this CV. We recommend to use this likelihood as the basis of communication with decision makers on how to decide on accepting or rejecting parameter estimates. (C) 2013 Elsevier Ltd. All rights reserved.
Genome-wide gene expression analysis of anguillid herpesvirus 1
Beurden, S.J. van; Peeters, B.P.H. ; Rottier, P.J.M. ; Davison, A.A. ; Engelsma, M.Y. - \ 2013
BMC Genomics 14 (2013). - ISSN 1471-2164 - 11 p.
channel catfish virus - time rt-pcr - dna microarray - european eel - murine gammaherpesvirus-68 - transcription - persistence - proteins - carp
Background Whereas temporal gene expression in mammalian herpesviruses has been studied extensively, little is known about gene expression in fish herpesviruses. Here we report a genome-wide transcription analysis of a fish herpesvirus, anguillid herpesvirus 1, in cell culture, studied during the first 6 hours of infection using reverse transcription quantitative PCR. Results Four immediate-early genes – open reading frames 1, 6A, 127 and 131 – were identified on the basis of expression in the presence of a protein synthesis inhibitor and unique expression profiles during infection in the absence of inhibitor. All of these genes are located within or near the terminal direct repeats. The remaining 122 open reading frames were clustered into groups on the basis of transcription profiles during infection. Expression of these genes was also studied in the presence of a viral DNA polymerase inhibitor, enabling classification into early, early-late and late genes. In general, clustering by expression profile and classification by inhibitor studies corresponded well. Most early genes encode enzymes and proteins involved in DNA replication, most late genes encode structural proteins, and early-late genes encode non-structural as well as structural proteins. Conclusions Overall, anguillid herpesvirus 1 gene expression was shown to be regulated in a temporal fashion, comparable to that of mammalian herpesviruses.
Viral shedding and emission of airborne infectious bursal disease virus from a broiler room
Zhao, Y. ; Aarnink, A.J.A. ; Cambra-Lopez, M. ; Fabri, T. - \ 2013
British Poultry Science 54 (2013)1. - ISSN 0007-1668 - p. 87 - 95.
respiratory-syndrome virus - newcastle-disease - united-kingdom - pig houses - chickens - transmission - immunosuppression - temperature - persistence - evaporation
1. The significance of airborne transmission in epidemics of infectious diseases in the livestock production industry remains unclear. The study therefore investigated the shedding route (faeces vs. exhaled air) of a vaccine strain of infectious bursal disease virus (IBDV) by broilers and the emission of airborne virus. 2. The experimental room contained 526 broilers which were orally inoculated at the age of 20¿d. The airborne virus was sampled by three different bioaerosol samplers: Andersen six-stage impactor, all-glass impinger (AGI-30) and OMNI-3000. 3. Infected broilers started to shed virus in faeces on d 5 post inoculation (PI), and stopped shedding on d 12 PI. The faecal virus remained detectable for at least two d after drying under broiler room conditions. No virus was detected in the air exhaled by broilers. 4. Airborne virus was collected on d 5, 8 and 12 PI at 20¿cm above the floor, and on d 8 and 12 PI in exhausted air. The emission rates of IBDV were 4·0 log10 50% tissue culture infectious dose (TCID50)/bird/d on d 8 PI, and 4·5 log10 TCID50/bird/d on d 12 PI. 5. We concluded that broilers shed IBDV mainly through their faeces. The presence of indoor airborne virus is associated with the viral presence in faeces. The successful recovery of airborne virus in exhausted air indicates there is a potential risk of virus spreading to the ambient environment via air.
Estimating degradation rates in outdoor stagnant water by inverse modelling with TOXSWA: a case study with prosulfocarb
Adriaanse, P.I. ; Boesten, J.J.T.I. ; Crum, S.J.H. - \ 2013
Pest Management Science 69 (2013)6. - ISSN 1526-498X - p. 755 - 767.
sediment/water systems - experimental ditches - pesticides - herbicide - behavior - biodegradation - persistence - simulation - sorption - field
Background The regulatory risk assessment of pesticides requires the assessment of exposure of aquatic ecosystems in small surface waters adjacent to agricultural fields. This exposure is predicted using simulation models, for which an important input parameter is the degradation rate in water. In regulatory dossiers, the decline rate in water from outdoor mesocosms is often available, but this rate encompasses more processes than degradation. Therefore, a procedure was designed for estimating the degradation rate in water that was suitable for mesocosm studies with limited datasets, e.g. datasets lacking site-specific sorption coefficients and relevant sediment properties. The procedure, based upon inverse modelling with TOXSWA, has been tested on a dataset for prosulfocarb in stagnant ditches. Results A degradation half-life in the ditch water of 2.9 days (20 °C) was found. This short half-life was to a significant extent accounted for by biodegradation rather than hydrolysis or photolysis. This half-life was considerably shorter than the half-life in the water layer of two laboratory water–sediment system experiments. Conclusion The estimation procedure resulted in a unique half-life for the degradation rate in water. Such outdoor mesocosm studies seem to be better suited to assessing the degradation rate in water in ditches than the conventional water–sediment studies.
Within-patch habitat quality determines the resilience of specialist species in fragmented landscapes
Ye, X. ; Skidmore, A.K. ; Wang, T. - \ 2013
Landscape Ecology 28 (2013)1. - ISSN 0921-2973 - p. 135 - 147.
metapopulation dynamics - population-dynamics - environmental variation - relative importance - isolation paradigm - extinction risk - effect size - long-term - heterogeneity - persistence
Patch geometry and habitat quality among patches are widely recognized as important factors affecting population dynamics in fragmented landscapes. Little is known, however, about the influence of within-patch habitat quality on population dynamics. In this paper, we investigate the relative importance of patch geometry and within-patch habitat quality in determining population dynamics using a spatially explicit, agent-based model. We simulate two mobile species that differ in their species traits: one resembles a habitat specialist and the other a habitat generalist. Habitat quality varies continuously within habitat patches in space (and time). The results show that spatial variation in within-patch quality, together with patch area, controls population abundance of the habitat specialist. In contrast, the population size of the generalist species depends on patch area and isolation. Temporal variation in within-patch quality is, however, less influential in driving the population resilience of both species. We conclude that specialist species are more sensitive than generalist species to within-patch variation in habitat quality. The patch area-isolation paradigm, developed in metapopulation theory, should incorporate variation in within-patch habitat quality, particularly for habitat specialists.
Different environmental drivers of highly pathogenic avian influenza H5N1 outbreaks in poultry and wild birds
Si, Y. ; Boer, W.F. de; Gong, P. - \ 2013
PLoS ONE 8 (2013)1. - ISSN 1932-6203
spread - virus - persistence - europe
A large number of highly pathogenic avian influenza (HPAI) H5N1 outbreaks in poultry and wild birds have been reported in Europe since 2005. Distinct spatial patterns in poultry and wild birds suggest that different environmental drivers and potentially different spread mechanisms are operating. However, previous studies found no difference between these two outbreak types when only the effect of physical environmental factors was analysed. The influence of physical and anthropogenic environmental variables and interactions between the two has only been investigated for wild bird outbreaks. We therefore tested the effect of these environmental factors on HPAI H5N1 outbreaks in poultry, and the potential spread mechanism, and discussed how these differ from those observed in wild birds. Logistic regression analyses were used to quantify the relationship between HPAI H5N1 outbreaks in poultry and environmental factors. Poultry outbreaks increased with an increasing human population density combined with close proximity to lakes or wetlands, increased temperatures and reduced precipitation during the cold season. A risk map was generated based on the identified key factors. In wild birds, outbreaks were strongly associated with an increased Normalized Difference Vegetation Index (NDVI) and lower elevation, though they were similarly affected by climatic conditions as poultry outbreaks. This is the first study that analyses the differences in environmental drivers and spread mechanisms between poultry and wild bird outbreaks. Outbreaks in poultry mostly occurred in areas where the location of farms or trade areas overlapped with habitats for wild birds, whereas outbreaks in wild birds were mainly found in areas where food and shelters are available. The different environmental drivers suggest that different spread mechanisms might be involved: HPAI H5N1 spread to poultry via both poultry and wild birds, whereas contact with wild birds alone seems to drive the outbreaks in wild birds.
MetaBase-the wiki-database of biological databases
Bolser, D.M. ; Chibon, P.Y.F.R.P. ; Palopoli, N. ; Gong, S. ; Jacob, D. ; Angel, V.D. Del; Swan, D. ; Bassi, S. ; Gonzalez, V. ; Suravajhala, P. ; Hwang, S. ; Romano, P. ; Edwards, R. ; Bishop, B. ; Eargle, J. ; Shtatland, T. ; Provart, N.J. ; Clements, D. ; Renfro, D.P. ; Bhak, D. ; Bhak, J. - \ 2012
Nucleic acids research 40 (2012)D1. - ISSN 0305-1048 - p. D1250 - D1254.
web services - life sciences - information - collection - persistence - catalog
Biology is generating more data than ever. As a result, there is an ever increasing number of publicly available databases that analyse, integrate and summarize the available data, providing an invaluable resource for the biological community. As this trend continues, there is a pressing need to organize, catalogue and rate these resources, so that the information they contain can be most effectively exploited. MetaBase (MB) (http://MetaDatabase.Org) is a community-curated database containing more than 2000 commonly used biological databases. Each entry is structured using templates and can carry various user comments and annotations. Entries can be searched, listed, browsed or queried. The database was created using the same MediaWiki technology that powers Wikipedia, allowing users to contribute on many different levels. The initial release of MB was derived from the content of the 2007 Nucleic Acids Research (NAR) Database Issue. Since then, approximately 100 databases have been manually collected from the literature, and users have added information for over 240 databases. MB is synchronized annually with the static Molecular Biology Database Collection provided by NAR. To date, there have been 19 significant contributors to the project; each one is listed as an author here to highlight the community aspect of the project.
Large Scale Marine Protected Areas for Biodiversity Conservation Along a Linear Gradient: Cooperation, Strategic Behavior or Conservation Autarky?
Punt, M.J. ; Weikard, H.P. ; Ierland, E.C. van; Stel, J.H. - \ 2012
Environmental and Resource Economics 53 (2012)2. - ISSN 0924-6460 - p. 203 - 228.
reserve site selection - taxonomic distinctiveness - relative abundances - diversity - design - model - persistence - objectives - networks - fishery
In this paper we investigate effects of overlap in species between ecosystems along a linear gradient on the location of marine protected areas (MPAs) under full cooperation, strategic behavior and conservation autarky. Compared to the full cooperation outcome, both strategic behavior and conservation autarky lead to under-investment in biodiversity protection. Under strategic behavior, however, we observe the additional problem of “location leakage” i.e. countries invest less in species protected by others. Conservation autarky eliminates location leakage; in ecosystems with partly overlapping species compositions at country borders it even induces MPAs that are too large from a global perspective. We also find that, in our setting of a linear gradient without migrating species, countries focus their conservation efforts on species unique to their own country and that these species are relatively well protected compared to common species.
Anguillid herpesvirus 1 transcriptome
Beurden, S.J. van; Gatherer, D. ; Kerr, K. ; Galbraith, J. ; Herzyk, P. ; Peeters, B.P.H. ; Rottier, P.J.M. ; Engelsma, M.Y. ; Davidson, A.J. - \ 2012
Journal of Virology 86 (2012)18. - ISSN 0022-538X - p. 10150 - 10161.
channel catfish virus - human cytomegalovirus transcriptome - european eel - structural proteins - genome sequences - gene-expression - koi herpesvirus - common carp - identification - persistence
We used deep sequencing of poly(A) RNA to characterize the transcriptome of an economically important eel virus, anguillid herpesvirus 1 (AngHV1), at a stage during the lytic life cycle when infectious virus was being produced. In contrast to the transcription of mammalian herpesviruses, the overall level of antisense transcription from the 248,526-bp genome was low, amounting to only 1.5% of transcription in predicted protein-coding regions, and no abundant, nonoverlapping, noncoding RNAs were identified. RNA splicing was found to be more common than had been anticipated previously. Counting the 10,634-bp terminal direct repeat once, 100 splice junctions were identified, of which 58 were considered likely to be involved in the expression of functional proteins because they represent splicing between protein-coding exons or between 5' untranslated regions and protein-coding exons. Each of the 30 most highly represented of these 58 splice junctions was confirmed by RT-PCR. We also used deep sequencing to identify numerous putative 5' and 3' ends of AngHV1 transcripts, confirming some and adding others by rapid amplification of cDNA ends (RACE). The findings prompted a revision of the AngHV1 genome map to include a total of 129 protein-coding genes, 5 of which are duplicated in the terminal direct repeat. Not counting duplicates, 11 genes contain integral, spliced protein-coding exons, and 9 contain 5' untranslated exons or, because of alternative splicing, 5' untranslated and 5' translated exons. The results of this study sharpen our understanding of AngHV1 genomics and provide the first detailed view of a fish herpesvirus transcriptome.
Diversity in biofilm formation and production of curli fimbriae and cellulose of Salmonella Thyphimurium strains of different origin in high and low nutrient medium
Castelijn, G.A.A. ; Veen, S. van der; Zwietering, M.H. ; Moezelaar, R. ; Abee, T. - \ 2012
Biofouling 28 (2012)1. - ISSN 0892-7014 - p. 51 - 63.
enterica serovar typhimurium - air-liquid interface - listeria-monocytogenes - multicellular morphotype - gastrointestinal-tract - agfd promoter - behavior - enterobacteriaceae - enteritidis - persistence
The biofilm forming behavior of 51 Salmonella Typhimurium strains was determined in Tryptone Soya Broth (TSB) and 20 times diluted TSB (1/20TSB) at 25°C and 37°C. The results indicated that biofilm forming behavior is influenced by environmental conditions and associated with the origin of the strains. Clinical, outbreak-associated and retail product isolates showed dense biofilm formation in both media at 25°C, and in TSB also at 37°C. However, industrial isolates only showed dense biofilm formation in 1/20TSB at 25°C. By enumeration of biofilm cells, LIVE/DEAD staining and SEM analysis of biofilms it was found that the ratio of cells and extracellular matrix is affected by environmental conditions. Indeed, the genes involved in curli fimbriae and cellulose production are highly induced during biofilm formation at 25°C in 1/20TSB. This indicates that these are important matrix components during biofilm formation in 1/20TSB at 25°C and that other factors contribute to biofilm formation of clinical, outbreak-associated and retail product isolates at 37°C and/or nutrient-rich conditions
Komkommerbontvirus in komkommer
Stijger, I. ; Hamelink, R. ; Ludeking, D.J.W. - \ 2011
komkommerbontvirus - besmetting - microbiële besmetting - komkommers - virussen - persistentie - gewasbescherming - cucumber green mottle mosaic virus - contamination - microbial contamination - cucumbers - viruses - persistence - plant protection
Informatieposter getiteld "Komkommerbontvirus in komkommer". Omdat chemische en biologische middelen het virus niet kunnen bestrijden, is komkommerbontvirus een terugkerend probleem
Spatial Planning of a climate adaptation zone for wetland ecosystems
Vos, C.C. ; Hoek, D.C.J. van der; Vonk, M. - \ 2010
Landscape Ecology 25 (2010)2010. - ISSN 0921-2973 - p. 1465 - 1477.
klimaatverandering - biodiversiteit - klimaatadaptatie - regionale planning - habitatfragmentatie - climatic change - biodiversity - climate adaptation - regional planning - habitat fragmentation - dynamic landscapes - conservation - metapopulation - persistence - networks - extreme - impacts - policy
Here we present a spatial planning approach for the implementation of adaptation measures to climate change in conservation planning for ecological networks. We analyse the wetland ecosystems of the Dutch National Ecological Network for locations where the effectiveness of the network might be weakened because of climate change. We first identify potential dispersal bottlenecks where connectivity might be insufficient to facilitate range expansions. We then identify habitat patches that might have a too low carrying capacity for populations to cope with additional population fluctuations caused by weather extremes. Finally, we describe the spatial planning steps that were followed to determine the best locations for adaptation measures. An essential part of our adaptation strategy is to concentrate adaptation measures in a ‘climate adaptation zone’. Concentrating adaptation measures is a cost-effective planning strategy, rendering the largest benefit per area unit. Measures are taken where abiotic conditions are optimal and measures to enhance the spatial cohesion of the network are taken close to existing areas, thus creating the highest possible connectivity with the lowest area demands. Another benefit of a climate adaptation zone is that it provides a spatial protection zone where activities that will have a negative impact on ecosystem functioning might be avoided or mitigated. The following adaptation measures are proposed within the climate adaptation zone: (1) link habitat networks to enable species to disperse from present to future suitable climate zones, (2) enlarge the carrying capacity by either enlarging the size of natural areas or by improving habitat quality to shorten population recovery after disturbances, (3) increase the heterogeneity of natural areas, preferably by stimulating natural landscape-forming processes, to avoid large synchronised extinctions after extreme weather events. The presented approach can be generalised to develop climate adaptation zones for other ecosystem types inside or outside Europe, where habitat fragmentation is a limiting factor in biodiversity responses to climate change.
Population dynamics under increasing environmental variability: implications of climate change for ecological network design criteria
Verboom, J. ; Schippers, P. ; Cormont, A. ; Sterk, M. ; Vos, C.C. ; Opdam, P.F.M. - \ 2010
Landscape Ecology 25 (2010). - ISSN 0921-2973 - p. 1289 - 1298.
klimaatverandering - biodiversiteit - habitatverbindingszones - vogels - climatic change - biodiversity - habitat corridors - birds - key-patch approach - habitat fragmentation - landscape - metapopulation - conservation - fluctuations - persistence - ranges
There is growing evidence that climate change causes an increase in variation in conditions for plant and animal populations. This increase in variation, e.g. amplified inter-annual variability in temperature and rainfall has population dynamical consequences because it raises the variation in vital demographic rates (survival, reproduction) in these populations. In turn, this amplified environmental variability enlarges population extinction risk. This paper demonstrates that currently used nature conservation policies, principles, and generic and specific design criteria have to be adapted to these new insights. A simulation shows that an increase in variation in vital demographic rates can be compensated for by increasing patch size. A small, short-lived bird species like a warbler that is highly sensitive to environmental fluctuations needs more area for compensation than a large, long-lived bird species like a Bittern. We explore the conservation problems that would arise if patches or reserve sizes would need to be increased, e.g. doubled, in order to compensate for increase in environmental variability. This issue has serious consequences for nature policy when targets are not met, and asks for new design criteria.
Transmission of wild-type and recombinant HaSNPV among larvae of Helicoverpa armigera (Lepidoptera: Noctuidae) on cotton.
Georgievska, L. ; Vries, R.S.M. ; Gao, P. ; Sun, X. ; Cory, J.S. ; Vlak, J.M. ; Werf, W. van der - \ 2010
Environmental Entomology 39 (2010)2. - ISSN 0046-225X - p. 459 - 467.
single-nucleocapsid nucleopolyhedrovirus - nuclear-polyhedrosis-virus - heliothis-armigera - trichoplusia-ni - baculovirus - field - infections - insecticides - persistence - pesticide
Horizontal transmission of insect viruses is a key factor in their cycling in agro-ecosystems. Here we study the transmission of the baculovirus HaSNPV among larvae of Helicoverpa armigera (Hübner) in cotton. Transmission of three HaSNPV genotypes was studied from larvae infected with a single virus genotype and from larvae infected with two different genotypes. Genotypes included a wild-type virus, an ecdysteroid UDP-glucosyltransferase (egt) deletion mutant (HaSNPV-LM2) with slightly enhanced speed of kill, and an egt-negative genotype that expresses a neurotoxin gene derived from the scorpion Androctonus australis Hector (HaSNPV-4A). The latter genotype has a substantially increased speed of kill. In three field experiments, the wild-type and egt deletion virus variants and a mixture of the two had similar rates of transmission. Transmission increased with density of infector insects and decreased with time lapsed since the inoculation of the infector larvae. Transmission of the neurotoxin expressing virus was lower than that of the other two genotypes in a glasshouse experiment. The studied genotypes of HaSNPV have significant differences in time to kill and virus yield, but we found no significant differences in rates of virus transmission at the crop level in the case of the egt deletion variant HaSNPV-LM2. Transmission of the transgenic virus genotype HaSNPV-4A was significantly reduced. Overall, differences in transmission between virus genotypes were subtler, and more difficult to detect with statistical significance, than effects of other factors, such as density of infectors and time delay between release of infectors and recipient caterpillars on the plant.
Komkommerbontvirus: Hygiëne en veranderingen in het virus
Stijger, I. ; Pham, K.T.K. ; Hamelink, R. ; Schenk, M.F. - \ 2010
komkommerbontvirus - komkommers - hygiëne - persistentie - ziektebestrijding - plantenziektebestrijding - protocollen - cucumber green mottle mosaic virus - cucumbers - hygiene - persistence - disease control - plant disease control - protocols
Van alle virussen die in komkommer kunnen besmetten, zorgt het komkommerbontvirus jaarlijks voor de grootste problemen. Omdat chemische en biologische middelen het virus niet kunnen bestrijden, is komkommerbontvirus een terugkerend probleem. In de loop van 2008/09 heeft Wageningen UR Glastuinbouw een hygiëneprotocol ontwikkeld met daarin de maatregelen die een teler kan nemen om besmetting met het virus te voorkomen. De teeltwisseling is daarbij de beste gelegenheid om de virusproblemen te verminderen. Komkommervirus is zeer persistent, zoals blijkt uit het feit dat virus kan overleven op kleding die gewassen wordt op 40 of 60 graden. Bij vergelijking van een aantal virusisolaten die in het verleden in Nederland verzameld zijn met recente praktijkmonsters, bleek dat er genetische verschillen bestaan