Search publications of the members of the Royal Belgian institute of natural Sciences
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Forest Succession Endangers the Special Ant Fauna of Abandoned Quarries along the River Meuse (Wallonia, Belgium)
- In Western Europe, old abandoned mining sites and quarries are often of high biodiversity and conservation value due to the presence of a number of endangered species. In the southern part of Belgium (Wallonia), many ancient quarries near the river Meuse are rather small and were abandoned from 50 to more than 100 years ago. In 2003, we collected 26 ant species by pitfall trapping in four of these quarries. In addition to common ones, several rare species, usually associated with mesomorphic to xeromorphic grasslands, were found in high numbers. Quarries undergoing forest succession were dominated by eurytopic species and by species typical of wet shadowy places, a fauna far less valuable in terms of nature conservation. Therefore, we suggest a management that halts further forest succession of open mesomorphic and xeromorphic habitat patches in these quarries. To assess and monitor the nature value of the ant fauna of these sites, we propose a so-called habitat preference approach, wherein each species is assigned to one of the following three habitat preference categories: (1) eurytopic, (2) bound to wet shadow-rich habitats, or (3) bound to dry open habitats. The stenotopic species of the last category are all endangered in Belgium and of high conservation value. The proportion of the total number of captured specimens included in the latter habitat preference category group is strongly reduced as scrub and tree encroachment advances. This proportion can therefore be used as a proxy to monitor the effects of management measures that prevent further forest succession.
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Functional richness of local hoverfly communities (Diptera, Syrphidae) in response to land use across temperate Europe
- Environmental change is not likely to act on biodiversity in a random manner, but rather according to species traits that affect assembly processes, thus, having potentially serious consequences on ecological functions. We investigated the effects of anthropogenic land use on functional richness of local hoverfly communities of 24 agricultural landscapes across temperate Europe. A multivariate ordination separated seven functional groups based on resource use, niche characteristics and response type. Intensive land use reduced functional richness, but each functional group responded in a unique way. Species richness of generalist groups was nearly unaffected. Local habitat quality mainly affected specialist groups, while land use affected intermediate groups of rather common species. We infer that high species richness within functional groups alone is no guarantee for maintaining functional richness. Thus, it is not species richness per se that improves insurance of functional diversity against environmental pressures but the degree of dissimilarity within each functional group.
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Heavy metal concentrations in the spiders Pirata piraticus (Clerck, 1757) and Clubiona phragmitis (C.L. Koch, 1843) along the Scheldt Estuary (Belgium)
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Heavy metal contents (Cd, Cu, Zn) in spiders (Pirata piraticus) living in intertidal sediments of the river Scheldt estuary (Belgium) as affected by substrate characteristics
- Metals are transferred into the food web by ground-dwelling organisms, among others. This study aimed to identify the most important factors that determine the bioavailability of heavy metals to the spider Pirata piraticus living in the intertidal sediments of the Scheldt estuary (Flanders, Belgium). At five locations, which represent a varying degree of metal contamination and salinity, the superficial layer of sediments was characterised for physico-chemical properties and heavy metal (Cd, Cu, Zn) content and extractability. Spiders were sampled at the same locations and analysed for Cd, Cu and Zn. Higher Cd, Cu and Zn contents were found in spiders on sites with lower total metal contents in the sediment. These sites were closest to the river mouth and were characterised by a higher salinity. Significant, positive correlations were found between the chloride content of the sediments and the Cd, Cu and Zn content of P. piraticus. Similarly, a strong relationship was observed between the ratio of exchangeable Cd and Zn to the total cation exchange capacity and the contents of these elements in P. piraticus. These field data indicated that salinity, cation exchange capacity and exchangeable metal contents were of most importance in determining bioavailability of heavy metals in these intertidal sediments. (C) 2002 Elsevier Science B.V. All rights reserved.
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How landscape structure, land-use intensity and habitat diversity affect components of total arthropod diversity in agricultural landscapes
- Agricultural intensification poses a serious threat to biodiversity as a consequence of increased land-use intensity, decreased landscape heterogeneity and reduced habitat diversity. Although there is interest in the preservation of total species richness of an agricultural landscape (gamma diversity), the effects of intensification have been assessed primarily by species richness at a local scale (alpha diversity). This ignores species richness between local communities (beta diversity), which is an important component of total species richness. In this study, measures of land-use intensity, landscape structure and habitat diversity were related to gamma, alpha and beta diversity of wild bees (Apoidea), carabid beetles (Carabidae), hoverflies (Syrphidae), true bugs (Heteroptera) and spiders (Araneae) within 16 local communities in 24 temperate European agricultural landscapes. The total landscape species richness of all groups was most strongly affected by increased proximity of semi-natural habitat patches. Bees also decreased in landscapes with a high intensity of farmland management, demonstrating additive effects of both factors. Separating total species diversity into components, the decrease in total species richness could be attributed primarily to a decrease in species diversity between local communities. Species richness of the local communities of all investigated groups decreased with increasing land-use intensity and, in the case of spiders, decreasing proximity of the semi-natural habitat patches. The effect of increased habitat diversity appeared to be of secondary importance to total species richness but caused a shift in the relative contribution of alpha and beta diversity towards the latter. Synthesis and applications. This study demonstrates that the effects of agricultural change operate at a landscape level and that examining species diversity at a local level fails to explain the total species richness of an agricultural landscape. The coincidence of patterns of beta diversity with those of gamma diversity emphasizes that such information is of crucial importance for the implementation and evaluation of restoration programmes aiming to restore sustainable countryside diversity. As local extinction processes in highly fragmented landscapes shape biodiversity, priority should be given to the conservation of diverse agricultural landscape remnants in Europe.
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Human-Induced Expanded Distribution of Anopheles plumbeus, Experimental Vector of West Nile Virus and a Potential Vector of Human Malaria in Belgium
- For the majority of native species, human-created habitats provide a hostile environment that prevents their colonization. However, if the conditions encountered in this novel environment are part of the fundamental niche of a particular species, these low competitive environments may allow strong population expansion of even rare and stenotopic species. If these species are potentially harmful to humans, such anthropogenic habitat alterations may impose strong risks for human health. Here, we report on a recent and severe outbreak of the viciously biting and day-active mosquito Anopheles plumbeus Stephens, 1828, that is caused by a habitat shift toward human-created habitats. Although historic data indicate that the species was previously reported to be rare in Belgium and confined to natural forest habitats, more recent data indicate a strong population expansion all over Belgium and severe nuisance at a local scale. We show that these outbreaks can be explained by a recent larval habitat shift of this species from tree-holes in forests to large manure collecting pits of abandoned and uncleaned pig stables. Further surveys of the colonization and detection of other potential larval breeding places of this mosquito in this artificial environment are of particular importance for human health because the species is known as a experimental vector of West Nile virus and a potential vector of human malaria.
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Hydrological regime and salinity alter the bioavailability of Cu and Zn in wetlands
- In the context of the European Water Framework Directive, controlled flooding of lowlands is considered as a potential water management strategy to minimise the risk of flooding of inhabited areas. However, due to historical pollution and overbank sedimentation, metal levels are elevated in most wetlands, which can cause adverse effects on the ecosystem's dynamics. Additionally, salinity affects the bioavailability of metals present or imported into these systems. The effect of different flooding regimes and salinity exposure scenarios (fresh- and brackish water conditions) on Cu and Zn accumulation in the oligochaete Tubifex tubifex (Muller, 1774) was examined. Metal mobility was closely linked to redox potential, which is directly related to the prevalent hydrological regime. Flooded, and thus more reduced, conditions minimized the availability of metals, while oxidation of the substrates during a drier period was associated with a rapid increase of metal availability and accumulation in the oligochaetes. (C) 2009 Elsevier Ltd. All rights reserved.
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Ideal Free distribution of fixed dispersal phenotypes in a wing dimorphic beetle in heterogeneous landscapes
- According to the ideal free distribution (IFD) theory, individuals that are able to perceive the quality of different patches in a landscape and disperse freely are expected to redistribute themselves proportionally to the carrying capacities of heterogeneous patches. Here, we argue that when dispersal is unconditional and genetically fixed, a coalition of sedentary and dispersing phenotypes can attain an IFD under spatio-temporally uncorrelated variation in fitness. This not only leads to a stable polymorphism of both dispersal phenotypes, but also implies that the number of dispersing individuals should on average be equal among patches and determined by the carrying capacity of the smallest local populations in the landscape. Differences in carrying capacity among patches are thus only reflected by changes in the number of sedentary individuals. Individual-based simulations show that this mechanism can be generalized over a wide range of spatio-temporal conditions and dispersal strategies. Moreover, these expectations are in strong agreement with empirical data on the density of both dispersal phenotypes of the wing dimorphic ground beetle Pterostichus vernalis within and among ten different landscapes. Hence, for the first time, these results demonstrate that this mechanism serves as a plausible alternative to the competition-colonization model to explain the spatial distribution of fixed dispersal phenotypes in heterogeneous landscapes. Understanding of the frequency distributions of individuals expressing discrete dispersal morphs moreover improves our predictive and management capabilities for a broad range of species, for which we currently typically rely on using mean dispersal rates.
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Indicators for biodiversity in agricultural landscapes: a pan-European study
- 1. In many European agricultural landscapes, species richness is declining considerably. Studies performed at a very large spatial scale are helpful in understanding the reasons for this decline and as a basis for guiding policy. In a unique, large-scale study of 25 agricultural landscapes in seven European countries, we investigated relationships between species richness in several taxa, and the links between biodiversity and landscape structure and management. 2. We estimated the total species richness of vascular plants, birds and five arthropod groups in each 16-km(2) landscape, and recorded various measures of both landscape structure and intensity of agricultural land use. We studied correlations between taxonomic groups and the effects of landscape and land-use parameters on the number of species in different taxonomic groups. Our statistical approach also accounted for regional variation in species richness unrelated to landscape or land-use factors. 3. The results reveal strong geographical trends in species richness in all taxonomic groups. No single species group emerged as a good predictor of all other species groups. Species richness of all groups increased with the area of semi-natural habitats in the landscape. Species richness of birds and vascular plants was negatively associated with fertilizer use. 4. Synthesis and applications. We conclude that indicator taxa are unlikely to provide an effective means of predicting biodiversity at a large spatial scale, especially where there is large biogeographical variation in species richness. However, a small list of landscape and land-use parameters can be used in agricultural landscapes to infer large-scale patterns of species richness. Our results suggest that to halt the loss of biodiversity in these landscapes, it is important to preserve and, if possible, increase the area of semi-natural habitat.
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Influence of flooding, salinity and inundation time on the bioavailability of metals in wetlands
- Controlled flooding of lowlands is considered as a potential water management strategy to minimize the risk of flooding of inhabited areas during high water periods. However, due to industrial activities, river water, sediments and soils are often contaminated with metals which may have adverse effects on the ecosystem's structure and functioning. Additionally, salinity may greatly affect the bioavailability and toxicity of metals present or imported into these systems. The effect of contaminated soils under different flooding and salinity exposure scenarios on the growth, reproduction and metal accumulation in the oligochaete Tubifiex tubitex (Muller, 1774) were examined. In these bioassays metal contaminated soils were flooded with water of different salinities (0 and 3 psu), and tested after 0, 6 and 12 months of permanent inundation. We indeed found that inundation time had significant decreasing effects on Cu and Zn accumulation; although initial accumulation of Cu and Zn was higher in the previously unflooded soil at the start of the flooding treatment, these differences seem to disappear after 6 months of permanent inundation. Moreover, the complex interaction between substrate type and salinity suggests that redox potential is probably of major importance. (C) 2006 Elsevier B.V. All rights reserved.
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Intensification of agriculture, landscape composition and wild bee communities: A large scale study in four European countries
- The impacts of agricultural practices and landscape composition on bee communities were investigated in 14 sites located in four Western European countries (Belgium, France, the Netherlands and Switzerland). Standardized interviews with farmers assessed agricultural practices in terms of agricultural inputs (nitrogen fertilization and pesticides), livestock density and crop types. The proportion of semi-natural habitats was calculated for each site. We showed negative effects of agricultural intensification on species richness, abundance and diversity of wild bees. By contrast, bee species richness increased with the amount of semi-natural habitats in the landscape. Using a co-inertia analysis, we found an opposition between two types of agricultural specialization: towards crop production or towards animal husbandry. Species richness, abundance and diversity of wild bees were greater in sites turned towards crop production. In these sites, flowering crops provided abundant food resources for bees whereas, in the other group of sites, intensive animal husbandry led to landscapes dominated by forage crops rather than flower-rich permanent grasslands. We also showed that bumblebees seemed to be less sensitive to agricultural intensification than solitary bees. (C) 2010 Elsevier B.V. All rights reserved.
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Is the hairy groove in the gibbosus male morph of Oedothorax gibbosus (Blackwall 1841) a nuptial feeding device?
- Oedothorax gibbosus (Blackwall 1841) (Erigoninae, Linyphiidae, Araneae) is a dwarf spider characterized by dimorphic males. There is a "gibbosus" male morph characterized by a hunch on the posterior third of the carapace, anterior to which is a hairy groove, and a "tuberosus" morph without these features. We observed several gustatorial courtship interactions by a gibbosus male morph and a conspecific female as well as a by a gibbosus male and a male of the closely related species, Oedothorax fuscus (Blackwall 1834). These interactions suggest that the hairy groove in the gibbosus male morph is a nuptial feeding device possibly under the influence of sexual selection. The interspecific interactions can possibly be interpreted as 'robbings' of the nuptial feeding. The interspecific interactions indicate that the cephalic structure of gibbosus probably does not function as a "lock and key" mechanism.
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Isolation and characterization of microsatellite loci in the dark bush cricket, Pholidoptera griseoaptera (Tettigoniidae)
- Twelve novel polymorphic microsatellite loci are presented for the dark bush cricket, Pholidoptera griseoaptera. All loci are polymorphic, with up to 37 alleles per locus. These microsatellites will be useful tools for studying the influence of landscape structure and land use intensity in agricultural landscapes on genetic diversity within and among populations of P. griseoaptera.
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Larval presence prediction through logistic regression: an early warning system against Mytilopsis leucophaeata biofouling
- Mytilopsis leucophaeata is a biofouling bivalve causing major problems in the cooling water system of BASF, Antwerp NV, Belgium, a large water-using industrial facility. This study aimed to develop a statistical model to predict the response of M. leucophaeata larvae to environmental conditions in estuarine ecosystems. Multiple logistic regression, taking into account temporal autocorrelation, was applied on a large dataset allowing the prediction of the probability of occurrence of M. leucophaeata larvae at BASF NV as a response to the environmental variables. The final model made it possible to predict larval presence in the water column solely by monitoring water temperature. The results from subsampling indicated that the model was stable. The model was tested with 2005 data, demonstrating a 98\% precise prediction of the occurrence of M. leucophaeata larvae in the water column, with a sensitivity of 100\% and a specificity of 97\%, even though autumn 2005 was exceptionally warm, which led to an extended presence of the larvae.
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Life cycle, reproductive patterns and their year-to-year variation in a field population of the wolf spider Pirata piraticus (Araneae, Lycosidae)
- Patterns of growth, phenology and reproduction were studied in a field population of the wolf spider Pirata piraticus from November 1997 until October 1998 and in June 1999 to unravel the intrapopulation variation and co-variation of these traits. Individuals of P. piraticus overwinter as juveniles of different instars while adults were found from the end of April until September. Strong year to year variation in the age and size of overwintering juveniles was present, resulting in a corresponding difference in adult size in the subsequent breeding season. The main period of reproduction occurred from May until August with larger individuals breeding earlier in the season. The size at which adults breed was also significantly different in the successive years. Clutch mass (cocoon mass), clutch volume and fecundity are dependent on the size of the female according to a weakly negative allometric relationship. The differences in those reproductive traits between the succesive years are therefore proportionate to the differences in female size. This was in clear contrast to egg size, a life history trait that shows much less variation and appears to be independent of female size. Therefore, egg size was not significantly different between spring 1998 and spring 1999. There is, however, some variation in fecundity due to egg size and number independent of female size. When corrected for female size, females with larger eggs produce relatively fewer eggs indicating a trade-off between these two reproductive characters.
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Local extinction processes rather than edge effects affect ground beetle assemblages from fragmented and urbanized old beech forests
- Local extinction of specialist species due to fragmentation is one of the major causes of biodiversity loss. Increased extinction rates in smaller fragments are expected to result from both smaller local population sizes, which increase the effect of environmental or demographic stochasticity, and increased edge effects. However, the relative effect sizes of these two factors are still poorly investigated. We attempt to disentangle these effects on ground beetle communities of temperate broadleaved woodland fragments situated in one of the most urbanized regions in Belgium. Assemblages were sampled along transects that extended from 30 m outside to 100 m inside both small and large historic forest fragments. Although species assemblages within the forest were highly distinct compared to those sampled outside the forest, species turnover along these transects was less pronounced within forest fragments indicating only weak edge effects. The magnitude of edge effects did not differ significantly between large and small fragments. However, larger differences in species composition were observed with respect to fragment size, wherein highly specialized species persisted only in the largest fragment. In sum, increased local extinction processes in smaller fragments, which led to a strong reduction of specialized and wingless forest species, appeared to be the most important factor that drives changes in species composition in this historic and fragmented woodland complex.
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Loss of genetic diversity and increased genetic structuring in response to forest area reduction in a ground dwelling insect: a case study of the flightless carabid beetle Carabus problematicus (Coleoptera: Carabidae)
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Metal accumulation in some terrestrial arthropods and its ecological and microevolutionary consequences in the wolf spider Pirata piraticus (Lycosidae, Araneae).
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Nematode communities of small farmland ponds
- The nematofauna of 14 farmland ponds, selected according to a gradient of surrounding agricultural land-use intensity, from five regions in North-West of Belgium were studied. The total nematode density (9-411 ind./10 cm(2) per pond), and especially the number of species (4-12 species per pond) was especially low in these ponds. In total, 17 genera of free-living benthic nematodes, belonging to 15 families, are identified. Tobrilus gracilis and Eumonhystera filiformis were the most common species and were found in 13 and 12 of the 14 sampled ponds, respectively. The genera Tobrilus and Eumonhystera jointly comprise 77\% of the total nematofauna. Consequently, the investigated water bodies were dominated by deposit feeding Monhysteridae and/or by chewing Tobrilidae. Diplogasteridae and Rhabditidae, normally related with eutrophic habitats, were almost absent. In order to explain the variation of total density, diversity, feeding-types composition and the individual density of the six most important species within ponds as well, sets of environmental variables were statistically selected. It was demonstrated that morphologically very similar species can show highly different ecological properties. The presence of a substantial mud layer and of an overall high level of eutrophication as well as the presence of possibly associated anaerobic conditions are put forward as the main factors explaining the observed low density and diversity. Total phosphate concentration and sediment characteristics seem to be the most important variables to explain the nematode community structure. However, a clear pattern of environmental variables, agricultural land use and nematode assemblages was not observed.
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Nematode communities of small pools in an agricultural landscape
