Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Mixed culture engineering for steering starter functionality
    Spuś, Maciej - \ 2016
    Wageningen University. Promotor(en): E.J. Smid; Tjakko Abee. - Wageningen : Wageningen University - ISBN 9789462578333 - 170
    bacteriophages - predation - microorganisms - starters - genetics - diversity - bacteriofagen - predatie - micro-organismen - zuursels - genetica - diversiteit

    Undefined mixed complex starter cultures are broadly used in Gouda-type cheese production due to their robustness to phage predation, resilience for changes in environmental conditions and aroma compounds production ability during ripening. These microbial communities of lactic acid bacteria prior their isolation and deposition in starter culture collections were continuously used at the farm-level production facilities. Thus, one can consider undefined mixed complex starters as domesticated microbial communities. The process of domestication was facilitated by humans who have been continuously repeating successful fermentations using part of previous batch as inoculum (i.e. back-slopping). Therefore, a term ‘community breeding’ can describe this human-driven domestication of microbial communities. Community breeding of a model complex starter Ur led to establishment of a simple two-species composition of Lactococcus lactis and Leuconostoc mesenteroides represented by, in total, 8 genetic lineages. At the same time, this simple microbial community displays a high degree of intraspecies diversity, presumably caused by evolutionary processes of horizontal gene transfer, genome decay and mutations. Such diversity at strain level is particularly interesting in the context of continuous bacteriophage predation pressure present in this microbial community. It is thought that constant-diversity (CD) dynamics, based on the ‘kill-the-winner’ principles, is operational in Ur starter at the strain level. According to CD model, the fittest strain(s), which feed on the most abundant substrate, will be selected against due to density-dependent phage predation. The control of the fittest strain abundance by bacteriophages opens space for differentiation of strains via eco-evolutionary feedbacks. In particular, strains of complex starter culture not only adapted to quickly acidify milk (via efficient consumption of lactose and protein to peptides degradation), but concurrently, to consume other substrates present in milk. In addition, throughout the process of community breeding microbe-microbe interactions between community members have evolved. These interactions have led to division of metabolic labor among strains present in the culture, and eventually to better starter microbial community functioning.

    The aim of this thesis was to investigate the factors impacting the formation of compositionally and functionally stable undefined mixed complex starter cultures to further use this knowledge in steering its functionality, and potentially in developing new strategies for robust starter culture design. To facilitate this study, well-characterized Ur culture strain isolates were used to systematically reconstitute the starter culture into multi-strain blends with increasing level of strain and genetic lineage diversity. The investigation of factors such as phage predation, level of strain and genetic lineage diversity as well as environmental conditions, was performed during experimental evolution studies in milk. The functionality of the (evolved) starter cultures was tested in an adapted lab-scale MicroCheese model system. The specific approach used in each of the research chapters is described below in more detail.

    Strains isolated from Ur starter culture were characterized in terms of their resistance against bacteriophages isolated from the same starter (Chapter 2). This test confirmed high diversity in phage resistance among strains belonging to different genetic lineages as well as among strains of the same lineage. Next, selected strains, which represented different levels of bacteriophage predation: resistant, moderately resistant, sensitive and no detectable sensitivity, were mixed in simple blends containing 4 strains representing 3 genetic lineages of Ur starter (3 such blends were designed). These blends were exposed to phage predation (one phage per blend) at the onset of prolonged sequential propagation experiment or propagated without phage addition (control). Throughout the serial propagation the genetic lineage composition was monitored. During the propagation of control blends we detected quick domination of a single lineage. This dominating lineage contained strains sensitive to phages. Genetic lineage level composition of the phage-challenged blends was much more dynamic suggesting the impact of phage predation. The relatively low strain diversity introduced in these blends was not high enough to sustain maximal diversity at the level of lineages.

    Chapter 3 describes a study using defined blends with higher complexity by extending the number of strains used. In total, 24 strains representing all 8 Ur starter lineages were exposed in sequential propagation experiment to a cocktail of 3 phages isolated from Ur starter. The propagation in milk of this multi-strain blend was executed for more than 500 generations and the abundance of genetic lineages was monitored throughout. Similarly as in the simple blends experiment, control blends were not exposed to bacteriophages. In control blends we observed a domination of one genetic lineage upon serial propagation, which resembles a periodic-selection-like (PS) behavior, where the fittest strains are dominating the microbial community and in result genetic-lineage diversity is being substantially reduced. In contrast, the composition of phage-challenged blends was again more dynamic than in control blends. In one of the phage-challenged blends behavior characteristic for a constant-diversity dynamics model was observed; throughout the serial transfer experiment, genetic lineage diversity was maintained by the presence of phage predation at relatively high level. In case of the second phage-challenged blend, due to a stochastic event, which likely caused a reduction in phage pressure, we observed a gradual recovery of the fittest strains, which again resembled a periodic-selection behavior. Therefore, phage predation, among other factors, can lead to shifts in microbial community population dynamics resulting in alternative stable states.

    The experimental evolution approach, resembling traditional process of back-slopping, was used in a Long-term experimental evolution of Undefined Mixed Starter Culture (LUMSC) study described in Chapter 4. The aim of this study was to investigate the compositional and functional stability ascribed to the undefined mixed Ur starter during enclosed prolonged propagation without any possible external influx of bacterial or phage material. Surprisingly, during this 1000-generation long experiment the enforced conditions of specific incubation temperature and propagation regime resulted in enrichment of previously not detected strain of Lactococcus laudensis. This strain was found to consume a by-product of metabolism of another strain present in the community, in particular, D-mannitol produced by Le. mesenteroides. Thus, a new putative interaction in the microbial community of the complex starter culture was found. This new interaction and the possible ability of L. laudensis to efficiently use peptides released by caseinolytic L. lactis ssp. cremoris resulted in a relatively high abundance of L. laudensis in all evolved LUMSC cultures. The high abundance of L. laudensis had a certain effect on the functionality of the cultures. The aroma profiles of model lab-scale milli-cheeses manufactured with LUMSC cultures, showed significant differences in formation of esters and alcohols when compared to cheeses produced with the original Ur starter. Moreover, L. laudensis strain was not only under the radar of previously used culture-dependent and culture-independent methods, but as well, under the radar of phage predation continuously present throughout the LUMSC experiment. This observation sheds new light on the possibility of how a strain can emerge to relatively high abundance in an enclosed serially propagated microbial community operating in accordance with CD dynamics model.

    Finally, the aspect of adaptation to environmental conditions was addressed by the study of an adjunct strain of Lactobacillus helveticus DSM 20075 described in Chapter 5. The aim was to develop a strain with increased autolytic capacity in conditions resembling the cheese matrix to possibly improve cheese ripening. The approach used here was based on a previously reported study, where the incubation of Lactococcus lactis MG1363 at high temperature resulted in spontaneous mutations causing stable heat-resistant and, in some cases, salt-hypersensitive phenotypes. In present study, after incubation of the Lb. helveticus DSM 20075 adjunct at different high temperatures (45-50 °C), heat-sensitive variants were recovered from plates. These variants were further characterized in terms of their growth rates at elevated temperatures (42-45 °C) and their autolytic capacity in low pH buffer with addition of NaCl. One of the variants (V50) showed substantially increased intracellular lactate dehydrogenase enzyme activity in the buffer suggesting its increased autolytic capacity. Next, both wild type and variant V50 were tested as adjuncts in lab-scale model milli-cheeses to determine their possible impact on the cheese aroma profiles. Indeed, adjunct strains, both WT and the variant, impacted the aroma profiles by producing benzaldehyde. In case of the variant strain the relative abundance of this compound was 3-fold higher. The applied strategy of incubating Lb. helveticus DSM20075 at high temperature resulted in specific, but different than in case of L. lactis MG1363, mutations suggesting another, yet to be elucidated, mechanisms for increasing the autolytic capacity of industrially-relevant strains. The approach of high-temperature incubation can be applied in dairy industry for the selection of (adjunct) cultures targeted at accelerated cheese ripening and aroma formation.

    In conclusion, the work presented in this thesis highlights the importance of co-evolution of strains in compositional and functional stability of the complex undefined mixed starter culture. In particular, the factors such as heterogeneity of bacteriophage resistance among highly related strains, microbe-microbe interactions and division of metabolic labor are crucial for optimal functioning of a complex starter microbial community. Further investigation of the factors impacting the composition of starter cultures is crucial to steer the functionality in a desired direction. With straightforward methods, such as changing the incubation temperature or the propagation regime it is possible to induce shifts in strain composition and thereby obtain cultures with new characteristics. Moreover, experimental evolution studies with microbial communities used in food fermentation can lead to the discovery of new strains with potentially new characteristics. Additionally, the study of microbial communities of starter cultures not only delivers industrially applicable knowledge but also reveals the action of basic principles in microbial ecology and evolution.

    The role of the starfish (Asterias rubens L.) predation in blue mussel (Mytilus edulis L.) seedbed stability
    Agüera García, A. - \ 2015
    Wageningen University. Promotor(en): Aad Smaal, co-promotor(en): Jeroen Jansen; Tim Schellekens. - Wageningen : Wageningen University - ISBN 9789462572164 - 170
    mytilus edulis - mossels - voortplanting - predatie - zaaibedden - predator prooi verhoudingen - waddenzee - aquacultuur - mytilus edulis - mussels - reproduction - predation - seedbeds - predator prey relationships - wadden sea - aquaculture


    Mussel beds are an important ecological component in the Wadden Sea. Mussels’ offspring settle massively in new suitable areas, forming seedbeds that may disappear again within months. The probability of a seedbed to survive the first winter is defined as seedbed stability; a definition that plays a very important role in the management of newly settled seedbeds. Many factors are important in the survival or extinction of seedbeds. Predation is thought to be particularly important during the first year after settlement and therefore key to survival. Many predators feed on mussel beds, but for most of them the potential to exterminate a seedbed is restricted by different factors such as prey selection or competition. Common starfish (Asterias rubens) are capable of concentrating/aggregating in high densities on mussel seedbeds making them an especially important factor limiting/affecting survival of mussel seedbeds. This study assesses the capacities of starfish as a mussel seed predator. It also provides tools and information to assess the risks of a seedbed being attacked and exterminated by starfish.

    In Chapter 2 the role of temperature and shading on winter predation was studied. The results showed that temperature limits feeding rate and feeding activity of starfish during winter. However, starfish feeding rate exhibited very high sensitivity to temperature changes. Light intensity affected both feeding rate and feeding activity. We conclude that starfish may not be an important factor destabilizing seedbeds during the average winter, but its importance may grow along with the increasing mean winter temperature due to climate change.

    In Chapter 3 the impact of salinity changes on predation performance and survival was assessed. Salinity is the main driver of species distributions in the Wadden Sea. Results show that salinity affected predation performance by reducing feeding activity and causing changes in prey selection. Moreover, as acclimation occurred, A. rubens predation performance improved in all treatments with survivors. We conclude that osmotic stress due to a salinity decreases determines A. rubens distribution, abundance and potential impact on the prey population. However this effect is influenced by the magnitude of the change in salinity and its timescale.

    In Chapter 4 the effect of tidal currents on predation rate was assessed, however, the chapter also tackles the role of hydrodynamic stress amelioration by mussels on the A. rubens population. The results suggest that mussels interact with their own predator beyond the role of food source, by ameliorating environmental stress, creating an additional dependence link between the foundation species and the predator, which potentially has major implications for ecosystem structure and stability.

    In Chapter 5, we assessed the role of mussel association with conspecifics at high densities on prey selection by A. rubens. We concluded that size selection does not always lead to an improvement in net profit. Size selection is a trade-off between energy yield and predation energy costs, which is affected by prey behaviour.

    The results of the prior chapters were integrated in Chapter 6 with field observations and literature to develop a simulation model. This model was designed to simulate growth of mussels and starfish, predation by starfish and mussel mortality. It can also be used to predict the likely effect of future environmental change scenarios on the potential impact of A. rubens on this important resource.

    In the general discussion, Chapter 7, previous literature, field data and the results from this thesis are summarised and reviewed to explain the spatial distribution of A. rubens in the Wadden Sea and the role of environmental conditions on A. rubens predation rate. Model simulations are used to answer the question: What is the role of A. rubens predation in mussel seedbed stability?

    Risico's van anticoagulantia rodenticides voor niet-doelsoorten en predatoren : een scan van beschikbare kennis in Europa en analyses in roofvogels uit Nederland
    Brink, N.W. van den - \ 2014
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2589) - 25
    knaagdieren - roofvogels - ecotoxicologie - predatie - voedselwebben - rodents - predatory birds - ecotoxicology - predation - food webs
    Knaagdierpopulaties kunnen zich lokaal ontwikkelen tot zeer hoge dichtheden en kunnen op deze manier een groot maatschappelijk probleem veroorzaken. Al eeuwen lang worden knaagdierplagen geassocieerd met de uitbraak van ziektes (waaronder de zwarte pest), maar ze kunnen ook economische schade toebrengen. Hierbij valt te denken aan het opeten en bederven van voedselvoorraden, transmissie van ziekteverwekkers tussen bijvoorbeeld boerderijen, terwijl tegenwoordig het knagen aan bedradingen e.d. ook een relevant probleem is. Het gedrag van deze dieren en het feit dat ze zeer snel in populatieomvang kunnen toenemen, maakt dat de bestrijding van knaagdieren continu aandacht behoeft. Er zijn verschillende methodes om knaagdieren te bestrijden.
    Harmonia axyridis: how to explain its invasion success in Europe
    Raak-van den Berg, C.L. - \ 2014
    Wageningen University. Promotor(en): Joop van Lenteren, co-promotor(en): Peter de Jong; Lia Hemerik. - Wageningen : Wageningen University - ISBN 9789462571037 - 221
    harmonia axyridis - organismen ingezet bij biologische bestrijding - geïntroduceerde soorten - invasieve exoten - predatie - voedingsgedrag - nederland - harmonia axyridis - biological control agents - introduced species - invasive alien species - predation - feeding behaviour - netherlands

    Abstract of the thesis entitled “Harmonia axyridis: how to explain its invasion success in Europe”

    After introduction as biological control agent of aphids, the multicoloured Asian ladybird Harmonia axyridis has established and spread in Europe. Harmonia axyridis is now regarded as an invasive species because its establishment had negative effects on non-target species, fruit production, and human health. Life history characteristics were studied in order to find an explanation for its invasion success.

    With a meta-analysis I showed that life-history traits of H. axyridis differed between Asian and invasive populations of H. axyridis. However, the greatest differences in development rate were observed at temperatures above 24°C, while at temperatures characteristic for spring and summer in northwestern Europe (17 to 24°C) invasive populations of H. axyridis do not differ from native Asian populations; thus, the invasive success cannot be attributed to a change in life history characteristics of the invasive population. Compared to native species European ladybirds (Adalia bipunctata, Coccinella septempunctata, and Propylea quatuordecimpunctata), H. axyridis develops slower and starts reproduction later, suggesting no competitive advantage for the invader.

    Additionally, life history characteristics were studied under field conditions. I showed that in northwestern Europe H. axyridis has a period of real diapause starting at the end of October and shifts to a quiescent state in December. This diapause is relatively short and weak compared with published data of native ladybirds. Moreover, it appears to have become shorter over the last decade. Thus, H. axyridis can become active rapidly when temperature rises in spring, but, nevertheless, it is not reported to be active earlier in the year than native species.

    Overwintering survival of H. axyridis in the Netherlands is between 71 and 88%. At five sample sites I found that ladybirds that were hibernating at the southwestern sides of buildings, where most aggregations of ladybirds were found, had a higher winter survival than ladybirds hibernating at other orientations. At sheltered sites survival was higher compared to exposed sites. A high overwintering survival results in a large post-hibernation population and a rapid population build-up in spring. Compared with most common native species, winter survival of H. axyridis is similar or higher.

    In this research, i.e. under semi-field conditions, immature survival of H. axyridis and A. bipunctata reached high levels, but survival was generally considerably higher for H. axyridis than for the native A. bipunc­tata. Under semi-field conditions with high food availability, no effect of the presence of H. axyridis on the survival, development, weight, and size of the native species A. bipunctata was found. Under natural conditions, however, situations of prey scarcity do occur, as aphid colonies are relatively short-lived.

    Additionally, I demonstrated that in absence of food under semi-field conditions, intraguild predation between C. septempunctata, A. bipunctata, and H. axyridis does occur, although the contact frequency is low. When two fourth instar larvae were placed together on a single leaf, at least one contact was made in 23–43% of the observations, depending on the tested species combination. When contacts between ladybirds do occur, H. axyridis larvae are the winners in contacts with larvae of the native species.

    Finally, I found that several natural enemies are starting to use H. axyridis as a host but are as yet not sufficiently abundant and/or effective to have a profound impact on populations of the invader. In the years 2003—2007 no natural enemies were found in ladybird samples. From 2008 onwards H. axyridis adults were infested by: Hesperomyces virescens fungi (summer and winter), Parasitylenchus bifurcatus nematodes (winter), Coccipolipus hippodamiae mites (winter), and Dinocampus coccinellae parasitoids (summer and winter).

    Summarising, the success­ful invasion of H. axyridis in the Netherlands cannot be explained by a change of the invasive H. axyridis populations in comparison with the native Asian population, but by a combi­nation of several characteristics: overwintering, immature survival, fecundity, longevity, number of generations per year, and intraguild predation. In comparison with native European ladybird species, H. axyridis survives better (in winter and the immature stages), it lays more eggs, has more generations per year, and lives longer: this results in a faster population growth than that of native ladybirds. Harmonia axyridis can potentially easily outnumber native species within a few years. Moreover, H. axyridis being a strong intra­guild predator, the slow immature development and late arrival at aphid colonies com­pared to native species is compensated by the ability of H. axyridis to feed on eggs, larvae, and pupae of other ladybirds, thereby completing its development.

    However, several facts, e.g. the quite stable diversity and abundance of ladybird species in Asia and the first evidence that natural enemies attack H. axyridis, suggest that the current situation in Europe may not be the terminal stage, but a transition to a new balance where native species are strongly reduced in abundance, but do not become extinct.

    Predation threats to the Red-billed Tropicbird breeding colony of Saba: focus on cats
    Debrot, A.O. ; Ruijter, M. ; Endarwin, W. ; Hooft, P. van; Wulf, K. - \ 2014
    Den Helder : IMARES (Report / IMARES Wageningen UR C011/14) - 53
    natuurlijke vijanden - vogels - predatie - katten - inventarisaties - caribisch gebied - natural enemies - birds - predation - cats - inventories - caribbean
    Feral domestic cats (Felis catus) are recognized as one of the most devastating alien predator species in the world and are a major threat to nesting colonies of the Red-billed Tropicbird (Phaethon aethereus), on Saba island, Dutch Caribbean. Cats and rats are both known to impact nesting seabirds and hence are both potential threats to the tropicbird on Saba. However, whereas the tropicbird has coexisted with rats for centuries, cats have only recently become a problem (since about 2000). Several studies from the region suggest that the tropicbird may be less-vulnerable to rats but cats have been unequivocally implicated in the depredation of tropicbird nests on Saba (unpublished data, Michiel Boeken). In this study we collected baseline data on cat and rat distribution, and cat diet and health. We also conducted 83 questionnaire interviews with Saba residents to assess their views on cats, rats, tropicbirds and the acceptability of different management options.
    De Wolf: getolereerd of geschoten?
    Wamelink, G.W.W. ; Lelieveld, G. ; Ottburg, F.G.W.A. ; Bodegom, P.M. van - \ 2013
    Vakblad Natuur Bos Landschap 2013 (2013)10. - ISSN 1572-7610 - p. 19 - 21.
    wolven - habitats - predatie - migratie - inventarisaties - centraal-europa - wolves - habitats - predation - migration - inventories - central europe
    De wolf is in aantocht, zowel vanuit het oosten als vanuit het zuiden. Waarom rukt hij op en is hij ineens zo succesvol? Wat eet hij? Welke invloed heeft hij op andere dieren? Vragen die een licht werpen op hoe we ons moeten voorbereiden. Omdat we dat niet kunnen op basis van eigen ervaring kijken we in dit artikel naar het buitenland en proberen een aantal van de meest prangende vragen over de wolf te beantwoorden op basis van literatuur
    De komst van de wolf naar Nederland
    Lammertsma, D.R. ; Groot Bruinderink, G.W.T.A. ; Jansman, H.A.H. ; Jacobs, M. - \ 2013
    Vakblad Natuur Bos Landschap 100 (2013). - ISSN 1572-7610 - p. 16 - 18.
    wolven - fauna - predatie - schade - financieren - wildbeheer - natuurbeleid - wolves - fauna - predation - damage - financing - wildlife management - nature conservation policy
    In de afgelopen tientallen jaren is de wolf begonnen aan een opmars door Europa, waarbij de Nederlandse grens steeds dichter wordt genaderd. De kans bestaat dan ook dat de wolf de komende jaren zal opduiken in Nederland. Deze ontwikkeling roept bij verschillende organisaties en bevolkingsgroepen uiteenlopende reacties op over de effecten op de natuur, de recreatie, de veeteelt, het faunabeheer en de veiligheid van de mens. Een belangrijke vraag is daarom hoe we met de eventuele komst van de wolf moeten omgaan. Alterra schreef in opdracht van het ministerie van Economische Zaken, de provincies en het Faunafonds een ‘factfinding study’.
    Is er ruimte voor wolven in Nederland?
    Potiek, A. ; Wamelink, G.W.W. ; Jochem, R. ; Langevelde, F. van - \ 2013
    Vakblad Natuur Bos Landschap 100 (2013). - ISSN 1572-7610 - p. 32 - 35.
    wolven - fauna - habitatfragmentatie - populatiedynamica - schattingen - predatie - inventarisaties - wolves - fauna - habitat fragmentation - population dynamics - estimates - predation - inventories
    De wolf nadert Nederland. Uit een modelstudie blijkt dat er genoeg geschikt leefgebied is voor mogelijk vijftig wolven. Door de aanwezigheid van ecoducten wordt de kans op een duurzame wolvenpopulatie aanzienlijk vergroot.
    Onderzoek naar de effectiviteit van de combinatie van twee beheermaatregelen voor rode Amerikaanse rivierkreeften : de Amerikaanse rivierkreeft in het Veenweidegebied: managementsamenvatting
    Boerkamp, A. ; Roessink, I. ; Giels, J. van; Ottburg, F.G.W.A. - \ 2012
    Wageningen : Alterra (Alterra-rapport 2244) - 92
    rivierkreeft - invasieve soorten - biologische bestrijding - predatie - vissen - experimenteel veldonderzoek - crayfish - invasive species - biological control - predation - fishes - field experimentation
    Dit onderzoek is uitgevoerd in opdracht van het ‘Hoogheemraadschap De Stichtse Rijnlanden’ (HDSR), i.s.m. Waternet, gemeente Woerden, STOWA en Team Invasieve Exoten. In deze studie wordt onderzocht wat de impact van de, uit de literatuur, twee meest veelbelovende beheers/bestrijdingsmaatregelen van invasieve kreeften is op een populatie rode Amerikaanse rivierkreeften (Procambarus clarkii). De twee maatregelen bestaan uit het wegvangen van adulte dieren en het inzetten van predatore vis om de aantallen van de jonge dieren te controleren. In dit experiment is gekozen voor paling als roofvis omdat dit de meest voor de hand liggende keuze was gezien het beheersgebied van HDSR en Waternet. Echter deze combinatie geeft in dit experiment niet de duidelijke resultaten die vooraf verwacht werden. Dit geeft in ieder geval aan dat de impact van predatore paling op kreeftenpopulaties niet sterk genoeg was om binnen 81 dagen duidelijke effecten te sorteren of dat deze impact van andere factoren (die niet of niet afdoende in de test vertegenwoordigd waren) afhankelijk is.
    Coexistence of fish species with strongly similar life histories - population dynamical feedback forces species to pick sides
    Schellekens, T. ; Kooten, T. van - \ 2011
    Yerseke : IMARES (Report / IMARES Wageningen UR C158/11) - 22
    vissen - aquatische ecosystemen - predatie - interspecifieke concurrentie - voedselwebben - diergemeenschappen - populatiedynamica - mariene ecologie - fishes - aquatic ecosystems - predation - interspecific competition - food webs - animal communities - population dynamics - marine ecology
    Fish generally grow several orders of magnitude between the larval and adult stage. Many ecological properties of organisms are related to body size, and hence small fish often have very different ecological roles than large conspecifics. This also implies that omnivory, the feeding on more than one trophic level by individuals of the same species, is a common phenomenon in fish. Intraguild predation is omnivory in its simplest form, where two species compete for the same resource, but one of the species can also eat its competitor. In models, persistence of both species in such a configuration is difficult to obtain. In marine fish communities however, it is observed routinely. One way in which persistence of omnivorous species can be established is by incorporating it as an ontogenetic diet shift, where small individuals of both species compete, and large individuals of one can feed on the small individuals of the others species. We show in this study that this mechanism can not only lead to persistence of a single omnivorous species, but also to persistence of multiple omnivorous species. This is possible given that the adults have sufficiently different diets. It is shown that, while adults of both species can feed both on small competitors or on the basic resource, due to the population dynamical feedback, one species will in practice act as a predator, while the other acts as prey. This way, a system with two omnivores in practice persists as a tritrophic system. Which of the species assumes which role depends on the specific community characteristics. We show here that by incorporating complex size-dependent feeding relationships in food webs, many more species may be able to coexist than is possible based on either species-level considerations or size spectrum models which do incorporate within-population size differences, but relate diet only to individual body size irrespective of species identity. The mechanism underlying our result may be part of the explanation why fish species with seemingly similar life histories do coexist in marine ecosystems.
    Weren van roofvogels uit de kippenuitloop
    Bestman, M.W.P. ; Liere, D. - \ 2011
    [Driebergen] : Louis Bolk Instituut (Publicatie / Louis Bolk Instituut nr. 2011-004 LbD) - 33 p.
    pluimveehouderij - roofvogels - predatie - wildbeheer - uitloop - biologische landbouw - vogelafweermiddelen - poultry farming - predatory birds - predation - wildlife management - outdoor run - organic farming - bird repellents
    In toenemende mate ondervinden pluimveehouders met uitloopkippen uitval door toedoen van roofvogels. Het merendeel van de in de literatuur beschreven afweermethoden is om uiteenlopende redenen ongeschikt. Na overleg met diverse deskundigen en belanghebbenden is besloten de volgende twee methoden uit te testen: het inspuiten van karkassen met een misselijkmakende stof en het onder stroom zetten van karkassen. Het onderzoek is gedaan op vijf pluimveebedrijven. De elektrische methode ging bij twee bedrijven niet gepaard met een wijziging in het aantal door roofvogels gedode kippen en bij één bedrijf ging het gepaard met een toename van de predatie door roofvogels. De roofvogels bleven eten van de kadavers die onder stroom stonden. De methode met de misselijk makende stof ging bij één bedrijf gepaard met een toename van de predatie door roofvogels en bij twee bedrijven met een afname van de predatie. Er is op basis van het geobserveerde gedrag, de consumptie van het kadavervlees en de uitval van kippen als gevolg van doding door roofvogels geen aanleiding om aan te nemen dat het toepassen van elektriciteit op een kadaver leidt tot een leereffect bij buizerds of haviken. De methode met de misselijk makende stof daarentegen lijkt wel van waarde omdat bij twee van de drie betrokken bedrijven de doding van kippen in de uitloop in de testfase minder bleek dan voor de behandelfase.
    Pristine wilderness of the Taimyr peninsula : 2008 expedition to the Pyasina Delta, Taimyr peninsula, Russian Federation
    Raad, J.A. ; Mazurov, Y.L. ; Ebbinge, B.S. - \ 2011
    Wageningen : Alterra (Alterra-rapport 2190) - 138
    alopex lagopus - branta bernicla - ganzen - lemmingen - wild - arctische gebieden - nestelen - predatie - larus - klimaatverandering - alopex lagopus - branta bernicla - geese - lemmings - wildlife - arctic regions - nesting - predation - larus - climatic change
    Revolutionary non-migratory migrants
    Jonker, M.R. - \ 2011
    Wageningen University. Promotor(en): Herbert Prins; Ron Ydenberg, co-promotor(en): Sip van Wieren. - [S.l.] : S.n. - ISBN 9789085859857 - 128
    ganzen - branta - migratie - oogstschade - predatie - nestelen - nederland - geese - branta - migration - crop damage - predation - nesting - netherlands

    In the migratory behaviour of the Barnacle Goose Branta leucopsis several changes have

    occurred over the past few decades. Barnacle geese breeding in Russia have delayed the

    commencement of spring migration with approximately one month since the 1980s,

    new populations have emerged in former stopover areas in the Baltic Sea region, and a

    non-migratory population has emerged in the wintering area in The Netherlands. This

    thesis aims to understand these changes.

    First, I studied the delay in commencement of spring migration. In the 1970s and 1980s,

    barnacle geese commenced spring migration half April, whereas spring migration now

    commences half May. I used a dynamic programming model to test three different

    possible explanations of delay in migration: 1) Climate change, because geese follow a

    green wave of fresh plant growth during spring migration, and are thus expected to be

    sensitive to increasing spring temperatures. 2) Competition for food during stopover

    because the population migrating to Russia has rapidly increased during the period in

    which the migration change occurred. 3) Predation danger during stopover because the

    number of avian predators such as White-tailed Eagles has drastically increased in the

    Baltic stopover area. The model showed that a delay of one month is adaptive in both

    the case of competition and predation danger. Strikingly, predation danger has received

    very little attention so far in goose studies.

    Migration strategy in geese is not genetically but culturally inherited, especially from

    parents to offspring via an extended period of parental care. Because this thesis focused

    on understanding migratory change, I focused on the parental care behaviour and the

    parent-offspring association because a change in migration was expected to be preceded

    by a change in the parent-offspring association. Because spring migration had delayed,

    the question arose whether the termination of parental care also had delayed. This

    would indicate a mechanistic link between the decision of commencement of migration

    and the termination of care, and would allow the barnacle geese to continue transmission

    of the migratory strategy to their offspring. Therefore, I quantified parental care

    throughout the season from autumn migration in Estonia to wintering in the Netherlands

    and through spring migration in Estonia. To quantify parental care, I compared

    parental geese (geese with offspring) and non-parental geese (geese without offspring).

    I showed that termination of parental care had not delayed but advanced as compared

    to the earlier situation, leaving a gap of two months between the estimated end of parental

    care (March) and the commencement of migration (May). This longer period of

    ‘adolescence’ and the accompanying exploratory behaviour may have strong influence

    on the amount of new colonization attempts by these abandoned offspring.

    In addition to delayed commencement of spring migration, also a non-migratory population

    emerged in the Netherlands. Life-history theory predicts that 1) higher expected

    Summary| 117

    future reproductive success leads to shorter parental care and 2) decreased benefits of

    parental care lead to shorter parental care. Both situations apply to the non-migratory

    population as compared to the migratory population of barnacle geese. Migration is

    a dangerous life-style, and has become even more dangerous as I showed earlier. Additionally,

    the non-migratory offspring encounters few dangers, making the benefits of

    parental care for the parents smaller. Hence, I compared the duration of parental care

    between migratory and non-migratory barnacle geese. To this end, I also quantified the

    parental care of the non-migratory population from autumn until spring. I showed that

    non-migratory barnacle geese take care of their offspring 21% shorter than migratory

    barnacle geese and terminate care already in November. This suggests a rapid adaptive

    adjustment of parental care coincident with altered migration.

    To understand the colonization history of the different populations of the Barnacle

    Goose, I developed a set of 384 Single Nucleotide Polymorphisms (SNP) specifically

    for the Barnacle Goose. By genotyping 418 individuals from Greenland, Spitsbergen,

    Russia, Sweden and the Netherlands (all major populations) I identified significant population

    structure. The results show that after previously having been separated, population

    admixture occurs now between all populations, indicated by significant linkage

    disequilibrium. Because the traditions of migratory behaviour promote differentiation

    between populations, this admixture suggested that these traditions had broken or had

    become weaker. We also show that the colonization of the Netherlands is not likely to

    have occurred by the Swedish population (which emerged ten years before the Dutch

    population emerged). The Russian and Dutch population are much more alike than the

    Swedish and Dutch population, indicating colonization of the Netherlands by formerly

    Russian barnacle geese.

    In the synthesis I showed that we can use life history trade-offs as indicators of environmental

    change. Based on the shortening of parental care I concluded that predation

    danger is a more likely explanation for the commencement of spring migration than

    food competition in the Baltic. I also showed that the shortening of parental care in

    the Barnacle Goose is not the norm in the Anatidae family, where the form of parental

    care is assumed to be very conservative. The observed change in our study showed that

    either the non-migratory barnacle geese adjusted their parental care unprecedentedly, or

    that the parental care systems in this family are poorly recorded or understood.

    Finally, I showed with a mechanistic model of cultural transmission of migratory behaviour

    that a delay in commencement of spring migration can explain sudden exploratory

    behaviour and colonization of new breeding areas at the cost of increased offspring

    mortality. The model also showed that the importance of culture on the transmission

    of migratory behaviour strongly affected the rate of exploration of new migratory


    Roofwantsen in roos, Thema: Doorontwikkelen duurzame gewasbescherming BO-12.03-003.01-002.04
    Pijnakker, J. - \ 2011
    rozen - gewasbescherming - duurzaamheid (sustainability) - plaagbestrijding met natuurlijke vijanden - agressie - predatie - capaciteit - roses - plant protection - sustainability - augmentation - aggression - predation - capacity
    Informatieposter over roofwantsen in roos (Thema: doorontwikkelen duurzame gewasbescherming). Bij biologische bestrijding in roos werken telers momenteel voornamelijk met roofmijten die diverse mijten en kleine insectenlarven eten. Ze zijn geschikt voor het bestrijden van spint, maar schieten tekort tegen trips en witte vlieg. De telers vragen om ‘agressievere’ natuurlijke vijanden (predatoren) tegen deze plaaginsecten
    Eindrapportage gele rozeluis in de teelt van aardbei onder glas
    Bloemhard, C.M.J. ; Linden, A. van der - \ 2008
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinbouw 193) - 28
    aardbeien - fragaria - rhodobium porosum - predatie - plagenbestrijding - coccinella - beauveria bassiana - aphidoletes aphidimyza - paecilomyces fumosoroseus - glastuinbouw - sluipwespen - strawberries - fragaria - rhodobium porosum - predation - pest control - coccinella - beauveria bassiana - aphidoletes aphidimyza - paecilomyces fumosoroseus - greenhouse horticulture - parasitoid wasps
    Van de vele soorten bladluizen die op aardbei kunnen voorkomen is de gele rozeluis Rhodobium porosum het moeilijkst chemisch te bestrijden. Dit onderzoek richt zich op de biologische bestrijding van de luis met natuurlijke vijanden als de sluipwespen, gaas en zweefvliegen en insectpathogene schimmels
    Precocial problems : shorebird chick performance in relation to weather, farming, and predation
    Schekkerman, H. - \ 2008
    University of Groningen. Promotor(en): T. Piersma; G.H. Visser. - Wageningen : Alterra - ISBN 9789090229799 - 228
    vogels - predatie - voedingsgedrag - kuikens - jonge dieren - weidevogels - agrarisch natuurbeheer - birds - predation - feeding behaviour - chicks - young animals - grassland birds - agri-environment schemes
    De afname van Nederlandse weidevogelpopulaties wordt mede veroorzaakt door problemen die kuikens bij het foerageren op insecten ondervinden. Het maaien van grasland leidt tot een sterke afname in het voedselaanbod, en een vervroeging van maaidatums in de afgelopen decennia heeft de foerageeromstandigheden voor kuikens sterk verslechterd. Tegelijkertijd zijn ook nog niet gemaaid graslandvegetaties minder geschikt geworden als kuikenhabitat door veranderingen in hun samenstelling en structuur, en is de predatiedruk op kuikens toegenomen. Het uitstellen van de maaidatum alleen is daardoor vaak niet meer voldoende om grutto’s voldoende jongen groot te laten brengen
    Een nieuw reactorconcept voor slibreductie met aquatische wormen
    Hendrickx, T.L.G. ; Elissen, H.J.H. ; Temmink, B.G. ; Buisman, C.J.N. - \ 2007
    Afvalwaterwetenschap 6 (2007)1. - ISSN 1568-3788 - p. 45 - 52.
    rioolslib - predatie - slib - wormen - afvalwaterbehandeling - afvalverwerking - waterorganismen - lumbricus - sewage sludge - predation - sludges - helminths - waste water treatment - waste treatment - aquatic organisms
    De behandeling van afvalwater resulteert in de productie van enorme hoeveelheden zuiveringsslib. In Nederland wordt dit slib voornamelijk verbrand. Een biologische aanpak voor het verminderen van de hoeveelheid slib die moet worden getransporteerd en verwerkt is de predatie door aquatische wormen. Tim Hendrickx, Hellen Elissen, Hardy Temmink en Cees Buisman beschrijven experimenten waarin de toepasbaarheid werd getest van een nieuw reactorconcept voor de reductie van slib met behulp van de aquatische oligochaet Lumbriculus variegatus
    Predatie bij weidevogels : op zoek naar de mogelijke effecten van predatie op de weidevogelstand, uitgebreide samenvatting
    Teunissen, W. ; Schekkerman, H. ; Willems, F. - \ 2006
    Beek-Ubbergen : SOVON Vogelonderzoek Nederland (Alterra-rapport 1292 samenvatting) - 24
    vogels - populaties - predatie - predatoren - nestelen - nederland - weidevogels - birds - populations - predation - predators - nesting - netherlands - grassland birds
    Weidevogels zijn in de laatste decennia sterk in aantal achteruitgegaan. Dit proces lijkt zich de laatste jaren zelfs nog te versnellen. Oorzaken voor deze negatieve ontwikkeling worden vooral gezocht in verlies van geschikt broedgebied voor weidevogels en de voortgaande intensivering van het agrarisch landgebruik. Daarnaast wordt predatie van legsels en kuikens de laatste jaren steeds vaker als probleem genoemd; volgens sommigen is het zelfs de hoofdoorzaak van de afnemende weidevogelpopulaties. Meningen daarover lopen echter zeer uiteen. SOVON, Alterra en Landschapsbeheer Nederland hebben daarom gezamenlijk een grootschalig onderzoek uitgevoerd naar het effect van predatie op de weidevogelpopulaties
    Improving natural pest suppression in arable farming: field margins and the importance of ground dwelling predators
    Alebeek, F.A.N. van; Kamstra, J.H. ; Kruistum, G. van; Visser, A.J. - \ 2006
    IOBC/WPRS Bulletin 29 (2006)6. - p. 137 - 140.
    bedrijfssystemen - predatie - overwintering - functionele biodiversiteit - agrobiodiversiteit - farming systems - predation - overwintering - functional biodiversity - agro-biodiversity
    Overwintering of soil dwelling arthropods and especially carabid beetles was much higher in unmown perennial field margins than in mown grass strips or barren crop fields. Over 200 generalist predators per m2 were trapped in field margin enclosures after hibernation. Predator exclusion experiments showed that high-density aphid colonies in May were reduced by 49% compared to predator-free conditions, both in field margins and in summer wheat crops. Over a 4 years period, aphid infestation levels in summer wheat and potatoes were 15%-65% lower in a farming system with a network of perennial field margins, compared to a system without field margins. However, Diamond back moth and slug damage in Brussels sprouts were higher in the system with field margins compared to the control system without margins.
    Biologische bestrijding trips in de bloemisterij: gedagsbeinvloedende stoffen en roofmijten voor de beheersing van trips in de bloemisterij onder glas
    Bulle, A.A.E. ; Boertjes, B.C. ; Bruin, J. ; Boogaard, M. ; Scholte-Wassink, G.M. ; Beerling, E.A.M. - \ 2006
    Wageningen : Praktijkonderzoek Plant en Omgeving (PPO) (Rapporten PPO Glastuinbouw ) - 44
    biologische bestrijding - organismen ingezet bij biologische bestrijding - predatie - roofmijten - afweermiddelen - insectenafweermiddelen - insectenbestrijding - thrips - biological control - biological control agents - predation - predatory mites - repellents - insect repellents - insect control - thrips
    Californische trips(Frankliniella occidentalis) is een belangrijke plaag in de glastuinbouw. In 2000 is een overkoepelend tripsproject gestart, waarin onderzoek van PPO Glastuinbouw en praktijkproeven van DLV Gewasbescherming op elkaar werden afgestemd. Dit resulteerde in onderzoek door PPO aan effectiviteit van bodemroofmijten en gedragsbeinvloedende stoffen. Uit de experimenten gedaan in het bodemroofmijtenonderzoek op de gewassen Impatiens, Petunia, Kalanchoe, Potchrysant, Saintpaulia en Yucca blijkt de bijdrage van bodemroofmijten aan de bestrijding van californische trips minimaal te zijn. De resultaten uit het onderzoek met gedragsbeïnvloedende stoffen laten zien dat er zeker mogelijkheden zijn om met behulp van 'natuurlijke stoffen' (GNO's) de tripsbestrijding te verbeteren. Enkele experimentele gedragsbeïnvloedende stoffen werden getest
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