Bargerveen Foundation

Nijmegen, Netherlands

Bargerveen Foundation

Nijmegen, Netherlands
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van Noordwijk C.G.E.,Bargerveen Foundation | van Noordwijk C.G.E.,Radboud University Nijmegen | Flierman D.E.,Bargerveen Foundation | Remke E.,Bargerveen Foundation | And 4 more authors.
Journal of Insect Conservation | Year: 2012

Semi-natural grasslands are increasingly grazed by large herbivores for nature conservation purposes. For many insects such grazing is essential for the conservation of their habitat, but at the same time, populations decrease at high grazing intensity. We hypothesised that grazing management may cause increased butterfly mortality, especially for life-stages with low mobility, such as hibernating caterpillars. To test this, we measured the effect of sheep grazing on overwinter larval survival. We used the Glanville fritillary (Melitaea cinxia), which has gregarious caterpillars hibernating in silk nests, as a model species. Caterpillar nests were monitored throughout the hibernating period in calcareous grassland reserves with low and high intensity sheep grazing and in an ungrazed control treatment. After grazing, 64 % of the nests at the high intensity grazing treatment were damaged or missing, compared to 8 and 12 % at the ungrazed and low intensity grazing treatment, respectively. Nest volume and caterpillar survival were 50 % lower at the high intensity grazing treatment compared to both ungrazed and low intensity grazing treatments. Nest damage and increased mortality were mainly caused by incidental ingestion of the caterpillars by the sheep. It is likely that grazing similarly affects other invertebrates, depending on their location within the vegetation and their ability to actively avoid herbivores. This implies that the impact of grazing strongly depends on the timing of this management in relation to the phenology of the species. A greater focus on immature and inactive life-stages in conservation policy in general and particularly in action plans for endangered species is required to effectively preserve invertebrate diversity. © 2012 The Author(s).

van Klink R.,University of Groningen | van der Plas F.,University of Groningen | van Noordwijk C.G.E.T.,Bargerveen Foundation | van Noordwijk C.G.E.T.,Radboud University Nijmegen | And 4 more authors.
Biological Reviews | Year: 2015

Both arthropods and large grazing herbivores are important components and drivers of biodiversity in grassland ecosystems, but a synthesis of how arthropod diversity is affected by large herbivores has been largely missing. To fill this gap, we conducted a literature search, which yielded 141 studies on this topic of which 24 simultaneously investigated plant and arthropod diversity. Using the data from these 24 studies, we compared the responses of plant and arthropod diversity to an increase in grazing intensity. This quantitative assessment showed no overall significant effect of increasing grazing intensity on plant diversity, while arthropod diversity was generally negatively affected. To understand these negative effects, we explored the mechanisms by which large herbivores affect arthropod communities: direct effects, changes in vegetation structure, changes in plant community composition, changes in soil conditions, and cascading effects within the arthropod interaction web. We identify three main factors determining the effects of large herbivores on arthropod diversity: (i) unintentional predation and increased disturbance, (ii) decreases in total resource abundance for arthropods (biomass) and (iii) changes in plant diversity, vegetation structure and abiotic conditions. In general, heterogeneity in vegetation structure and abiotic conditions increases at intermediate grazing intensity, but declines at both low and high grazing intensity. We conclude that large herbivores can only increase arthropod diversity if they cause an increase in (a)biotic heterogeneity, and then only if this increase is large enough to compensate for the loss of total resource abundance and the increased mortality rate. This is expected to occur only at low herbivore densities or with spatio-temporal variation in herbivore densities. As we demonstrate that arthropod diversity is often more negatively affected by grazing than plant diversity, we strongly recommend considering the specific requirements of arthropods when applying grazing management and to include arthropods in monitoring schemes. Conservation strategies aiming at maximizing heterogeneity, including regulation of herbivore densities (through human interventions or top-down control), maintenance of different types of management in close proximity and rotational grazing regimes, are the most promising options to conserve arthropod diversity. © 2014 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.

Verberk W.C.E.P.,Radboud University Nijmegen | Verberk W.C.E.P.,Bargerveen Foundation | Verberk W.C.E.P.,University of Plymouth | Van Noordwijk C.G.E.,Radboud University Nijmegen | And 4 more authors.
Freshwater Science | Year: 2013

The use of species traits in basic and applied ecology is expanding rapidly because trait-based approaches hold the promise to increase our mechanistic understanding of biological responses. Such understanding could transform descriptive field studies in community ecology into predictive studies. Currently, however, trait-based approaches often fail to reflect species-environment relationships adequately. The difficulties have been perceived mainly as methodological, but we suggest that the problem is more profound and touches on the fundamentals of ecology and evolution. Selection pressures do not act independently on single traits, but rather, on species whose success in a particular environment is controlled by many interacting traits. Therefore, the adaptive value of a particular trait may differ across species, depending on the other traits possessed by the species and the constraints of its body plan. Because of this context-dependence, trait-based approaches should take into account the way combinations of traits interact and are constrained within a species. We present a new framework in which trade-offs and other interactions between biological traits are taken as a starting point from which to develop a better mechanistic understanding of species occurrences. The framework consists of 4 levels: traits, trait interactions, trait combinations, and life-history strategies, in a hierarchy in which each level provides the building blocks for the next. Researchers can contribute knowledge and insights at each level, and their contributions can be verified or falsified using logic, theory, and empirical data. Such an integrated and transparent framework can help fulfill the promise of traits to transform community ecology into a predictive science. © 2013 by The Society for Freshwater Science.

Verberk W.C.E.P.,Radboud University Nijmegen | Verberk W.C.E.P.,Bargerveen Foundation | Verberk W.C.E.P.,University of Plymouth | van den Munckhof P.J.J.,Staatsbosbeheer | Pollux B.J.A.,Wageningen University
Aquatic Ecology | Year: 2012

Acute exposure to iron can be lethal to fish, but long-term sublethal impacts of iron require further study. Here we investigated whether the spatial and temporal distribution (1967-2004) of two closely related species of stickleback matched the spatial distribution of iron concentrations in the groundwater. We used the 'Northern Peel region', a historically iron-rich peat landscape in The Netherlands as a case study. This allowed us to test the hypothesis that niche segregation in two closely related species of stickleback occurred along a physiological axis. Patterns in stickleback occurrence were strongly associated with spatial patterns in iron concentrations before 1979: iron-rich grid cells were avoided by three-spined stickleback (Gasterosteus aculeatus, Linnaeus 1758) and preferred by nine-spined stickleback (Pungitius pungitius, [Linnaeus, 1758]). After 1979, the separation between both sticklebacks became weaker, corresponding to a decreased influence of local groundwater on stream water quality. The way both species changed their distribution in the field provides a strong indication that they differ in their susceptibility to iron-rich conditions. These observed differences correspond with differences in their respiration physiology, tolerance of poor oxygen conditions and overall life-history strategy documented in the literature. Our results exemplify how species can partition niche along a non-structural niche axis, such as sublethal iron-rich conditions. Other fish species may similarly segregate along concentration gradients in iron, while sublethal concentrations of other metals such as copper may similarly impact fish via respiratory impairment and reduced aerobic scope. © 2012 The Author(s).

Van Oosten H.H.,Bargerveen Foundation | Van Oosten H.H.,Radboud University Nijmegen | Emtsev A.A.,Surgut State University
Ardea | Year: 2013

The Yellow Wagtail Motacilla flava consists of about 18 taxa whose taxonomic relationships are unclear. Some authors elevate 11 taxa to species based on often characteristic nuptial plumages of males, whereas others recognize two species based on molecular data. Hybridization is a regular event but with intriguingly varying intensity between different taxa. In spite of breeding generally in damp fields, their breeding habitat is actually rather diverse, which offers an opportunity for ecological segregation by breeding habitat. Indeed, some authors describe habitat differences between taxa but others do not. Two sympatrically occurring taxa are thunbergi and beema in European Russia and Western Siberia. In this study we describe their breeding habitat and determine whether this differs between taxa. We aimed to determine whether breeding habitat could be an ecological factor for sub-specific segregation in this part of their breeding range. We found strong indications for segregated breeding, despite the rather limited dataset: thunbergi occurred in bogs as a breeding bird and beema was dominantly found breeding in floodplain meadows. On one location bog and floodplain were separated by only 1.5-2 km of forest, yet here too only thunbergi occurred on the bog and beema on floodplain meadows. Following recent molecular taxonomic findings our thunbergi might very well concern plexa, belonging to the eastern species. As beema is assigned to the western species, the observed spatial segregation between plexa and beema may be representative of habitat separation of the western and eastern species in areas where they occur sympatrically. Large scale segregated breeding due to different habitat preferences could have consequences for taxonomic interpretations within the M. flava complex.

Vermonden K.,Radboud University Nijmegen | Vermonden K.,Copenhagen University | Brodersen K.P.,Copenhagen University | Jacobsen D.,Copenhagen University | And 4 more authors.
Journal of the North American Benthological Society | Year: 2011

Interest in the biodiversity value of urban waters is growing. Understanding key ecological processes is essential for effective management of these aquatic ecosystems. Our paper focuses on identifying the key factors that structure chironomid assemblages, such as water quality and dredging, in urban waters strongly influenced by seepage of large rivers. Chironomid assemblages were studied in urban surface-water systems (man-made drainage ditches) in polder areas along lowland reaches of the rivers RhineMeuse in The Netherlands. Multivariate analysis was used to identify the key environmental factors. Taxon richness, Shannon index (H′), rareness of species, and life-history strategies at urban locations were compared with available data from similar man-made water bodies in rural areas, and the effectiveness of dredging for restoring chironomid diversity in urban waters was tested. Three different chironomid associations were distinguished by Two-Way Indicator Species Analysis. Variation within and among chironomid associations were significantly related to substrate (sludge layer and substrate type: sand vs clay), % cover of lemnids, submerged vegetation, filamentous algae, and water transparency. Chironomid taxon richness and H′ were similar in urban and rural waters, probably because of their similar hydrologic, morphologic, and water-quality conditions and their similar dredging and weed-control regimes. Rareness was slightly higher in urban than in rural waters. In urban water systems, chironomid taxon richness was negatively related to sludge layer and % cover of lemnids. Dredging changed chironomid species composition, and increased taxon richness and life-history strategies indicative of good O2 conditions. Therefore, dredging can be regarded as an effective measure to restore diversity of chironomid communities in urban waters affected by nutrient-rich seepage or inlet of river water. © 2011 by The North American Benthological Society.

Van Noordwijk C.G.E.,Bargerveen Foundation | Van Noordwijk C.G.E.,Radboud University Nijmegen | Boer P.,Gemene Bos 12 | Mabelis A.A.,Wageningen University | And 4 more authors.
Ecological Indicators | Year: 2012

Species' life-history traits underlie species-environment relationships. Therefore, analysis of species traits, combined into life-history strategies, can be used to identify key factors shaping the local species composition. This is demonstrated in a case-study on ants in chalk grasslands. We developed four life-history strategies based on traits related to reproduction, development, dispersal and synchronization that are documented in the literature. These theoretical strategies reflect different responses to certain environmental conditions. They can be characterized as generalists (G), poor dispersers (D), species whose distribution is limited to sites with high food availability (F) and species that are restricted to sites with high soil temperatures during nest founding (T). Next, we tested whether the occurrence of these strategies differed between six Dutch chalk grasslands and four reference sites situated in Germany and Belgium. We found significant differences in species numbers between sites for strategies D and T but not for strategies F and G. The differences could be explained by differences in connectivity and microhabitat conditions; species richness of strategy D decreased exponentially with increasing distance to the next nearest chalk grassland, while summer soil temperature strongly affected species richness of strategy T. From these relationships we could successfully identify the most relevant bottlenecks for the occurrence of both of these strategies in Dutch chalk grasslands. Management recommendations resulting from this analysis include adapting the management timing in Dutch chalk grasslands and focussing on counteracting habitat isolation. With this case-study we demonstrate that the life-history strategy approach is a valuable alternative to approaches that try to identify key factors by analysing the variation in environmental parameters. The main advantage of the presented alternative is the focus on mechanistically understanding species responses, allowing a comparison of processes rather than occurrences of single species. © 2011 Elsevier Ltd.

Verberk W.C.E.P.,Bargerveen Foundation | Verberk W.C.E.P.,Radboud University Nijmegen | Leuven R.S.E.W.,Radboud University Nijmegen | van Duinen G.A.,Bargerveen Foundation | And 3 more authors.
Basic and Applied Ecology | Year: 2010

Restoration management frequently focuses on recreating suitable environmental conditions for a 'target vegetation'. This approach neglects the importance of habitat diversity and spatial configuration for individual species. Here, we investigate the role of environmental heterogeneity in a restoration context and report the response of aquatic macroinvertebrates to re-wetting measures, which were taken to mitigate desiccation in a bog landscape. Because only parts of the study area were affected by re-wetting measures, changes in aquatic macroinvertebrates could be compared between re-wetted and non-re-wetted parts. In addition, species were grouped into life-history strategies to test whether the invertebrate response differed between functional species groups. Total species numbers declined in the re-wetted parts and invertebrate assemblages became more similar both in terms of species and life-history strategies. These results indicate that large-scale re-wetting caused a functional homogenization. Changes in environmental conditions following re-wetting could be consistently related to changes in strategy composition. Retention of rainwater decreased the influence of groundwater. Here species increased that are adapted to physiological stress as well as those employing risk spreading, which indicates that environmental conditions had become harsher and less predictable. In contrast, reduced drainage locally increased groundwater influence, with life-history strategies indicating enhanced predictability of environmental conditions. Importantly, such conditions also characterise lagg zones and transitional mires in pristine raised bog landscapes, which are hotspots for biodiversity. Thus, while large-scale re-wetting decreased environmental heterogeneity, increasing the supply of groundwater seems a more promising restoration strategy for aquatic invertebrates in degraded peatlands. © 2010 Gesellschaft für Ökologie.

van Kleef H.H.,Bargerveen Foundation | Jongejans E.,Radboud University Nijmegen
Aquatic Invasions | Year: 2014

Pumpkinseed (Lepomis gibbosus) is listed among the most invasive fish species and has been demonstrated to have adverse impact on native species when present in high numbers. However, not all introductions result in high density populations. There are several possible underlying mechanisms behind this variation in population density (e.g. water quality, availability of nesting substratum and biotic interactions), but their relative importance remains poorly known. With this in mind, we studied vital rates (i.e. growth, maturation and reproduction) of pumpkinseed in 19 isolated standing waters of different pumpkinseed density. The fish were collected in early summer to determine their density, sex, age, growth and reproductive effort as well as environmental variables (i.e. availability of nesting substratum, acidity, nutrient concentrations, fish assemblage structure). To construct a population projection model with which to assess the relative importance of each vital rate for the growth of the populations, a stable population structure was assumed. Most environmental variables that affected vital rates (e.g. pH effect on individual growth) had little effect on population growth, or the associations were spurious (e.g. the negative effect of nesting substratum availability on gonad production). The environmental effects were dictated by a strong density dependent feedback of pumpkinseed density on the growth of age 2 fish, and gonad size and maturation state. This finding has important repercussions for management of pumpkinseed invasions: if only part of the population is removed or if complete eradication is followed by a re-introduction, then the population will rapidly recover to its former size. It was not possible to identify environmental drivers of pumpkinseed survival because the data had to be pooled across populations in order to estimate survival rates. However, a negative correlation was found between pumpkinseed and predator density, indicating that predator-induced mortality may be key in determining pumpkinseed invasiveness. Although the measure still needs thorough evaluation, introduction of native piscivores, especially northern pike (Esox lucius), may be a suitable way to prevent pumpkinseed from becoming the dominant species and reduce damage to local biodiversity. © 2014 The Author(s). Journal compilation.

van Kleef H.,Bargerveen Foundation | van Kleef H.,Radboud University Nijmegen | Verberk W.C.E.P.,Radboud University Nijmegen | Kimenai F.F.P.,Radboud University Nijmegen | And 3 more authors.
Basic and Applied Ecology | Year: 2015

Acidification has led to a strong decline of species characteristic of shallow soft-water lakes. In spite of reductions in acidifying deposition, natural recovery of biodiversity is modest or even absent, suggesting that the impact of acidification is difficult to reverse. We compared recovery from acidification in non-restored and restored lakes using data from 1983 and 2004. In restored lakes, accumulated organic matter was removed and alkaline water was supplied, resulting in an increase in pH and alkalinity and a decrease in ammonium, sulphur and aluminium. For evaluation of biotic changes we selected chironomid larvae (Diptera). In restored lakes, rarefied species richness increased, chironomid species composition changed and responses of chironomid taxa and their life-history strategies indicated a shift towards pre-acidification assemblages. Species adapted to dynamic and stressful environments decreased in favour of those with life history strategies suitable for more benign environments. In non-restored lakes, chironomid response did not indicate a recovery, despite an improved water chemistry in terms of decreased acidity and sulphur (not ammonium and aluminium). Instead, stressful conditions related to oxygen shortage became more prevalent as a decrease was observed in the chironomids least adapted to periods with low oxygen availability. Acidification has inhibited decomposition, resulting in the accumulation of organic material. Natural recovery from acidification resumed and increased the decomposition of this accumulated organic material, resulting in release of nutrients, consumption of oxygen and a decline of sensitive bottom-dwelling fauna such as chironomids. Therefore, active restoration by removal of accumulated organic matter from sand bottoms is essential for a recovery of chironomid assemblages. © 2015 Gesellschaft für Ökologie.

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