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Functional richness of local hoverfly communities (Diptera, Syrphidae) in response to land use across temperate Europe
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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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Experimental exposure to cadmium affects metallothionein-like protein levels but not survival and growth in wolf spiders from polluted and reference populations
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Both local adaptation and acclimation in tolerance mechanisms may allow populations to persist under metal pollution. However, both mechanisms are presumed to incur (energetic) costs and to trade-off with other life-history traits. To test this hypothesis, we exposed Pardosa saltans (Lycosidae) spiderlings originating from metal-polluted and unpolluted sites to a controlled cadmium (Cd) treatment, and compared contents of metal-binding metallothionein-like proteins (MTLPs), internal metal concentrations, and individual survival and growth rates with a reference treatment. While increased MTLP concentrations in offspring originating from both polluted and unpolluted populations upon exposure indicates a plastic tolerance mechanism, survival and growth rates remain largely unaffected, independent of the population of origin. However, MTLP and Cd concentrations were not significantly correlated. We suggest that MTLP production may be an important mechanism enabling P. saltans populations to persist in ecosystems polluted with heavy metals above a certain level. (C) 2010 Elsevier Ltd. All rights reserved.
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Differentiation between two salt marsh beetle ecotypes: Evidence for ongoing speciation
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The plausibility of trait divergence under divergent natural selection in the presence of gene flow in natural populations is a contentious issue in evolutionary research. Its importance lies in the fact that this process is thought to be one of the key triggers in ecological speciation in which a species splits into ecologically distinct forms when separate niches are occupied. in this study we demonstrate strong genetic divergence at the IDH1 locus between pond- and canal-inhabiting individuals of the salt marsh beetle Pogonus chalceus from the Guerande salt fields. Moreover, wing size, a trait that has a heritable basis in this species, was significantly larger in the pond populations, which is in concordance with the unstable nature of this habitat. The relationship between IDH1 allele frequencies and wing size variation was consistent with patterns seen across western European populations. By means of neutral allozymes and microsatellites we detected a small but significant degree of sexual isolation between ecotypes. We conclude that speciation is ongoing and that divergence reflects a balance between selection and gene flow.
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Differences in geographic distribution and habitat of some cryptic species in the Pardosa lugubris group (Lycosidae, Araneae) in Belgium
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The habitat and distribution of some closely related species of the P. lugubris s.l. group in Belgium are described to contribute to our understanding of the coexistence and speciation of these 'cryptic' species. With a few exceptions, P. lugubris has its main distribution in the lower part of Belgium where it occurs on sandy, nutrient poor soils. P. saltans occurs widely in Belgium except for in the Campine region where the species is totally absent. P. alacris was only found at three localities where limestone outcrops are present. The habitat of P. lugubris is pine and birch forests while in Fagus woodlands, only P. saltans was found. In Quercus forests, both species were found, often in mixed populations. A combination of micro- and macroclimatological features and habitat characteristics cause the differences in distribution of these species.
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Can multiple mating compensate for slower development and shorter adult life in a male dimorphic dwarf spider?
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Oedothorax gibbosus (Blackwall, 1841) is a dwarf spider characterized by the occurrence of a male dimorphism: the tuberosus male does not show any remarkable differentiation at the dorsal side of the carapace; the gibbosus morph on the contrary has a hunch behind the eye region, with a transversal groove densely clothed with hairs. These structures play an important function in the gustatorial courtship, being the uptake of secretions by the female from a body part of the male during courtship. Based on standardized survival experiments we show that tuberosus has a greater overall survival strength for different humidity levels than gibbosus. The two male morphs of O. gibbosus also have a different mating strategy: tuberosus as well as gibbosus copulate with virgin females, but gibbosus copulates significantly more with already inseminated females. Because of this strategy gibbosus secures its offspring notwithstanding the faster development, the longer adult life and the greater overall survival strength of tuberosus. (C) 2004 The Linnean Society of London
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Absence of cadmium excretion and high assimilation result in cadmium biomagnification in a wolf spider
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Cd biomagnification in the terrestrial food chain appears to be dependent on the physiological properties of the organisms rather than on their trophic level. Although high Cd body burdens in spiders from the field have been reported many times, experimental verification of the key factors that determine the rate of cadmium accumulation is lacking. We investigated the cadmium assimilation rate in the common wolf spider Pirata piraticus fed with contaminated fruit flies. Spiders were fed for 42 days with contaminated flies, followed by a detoxicification period of 28 days. Every 14 days, a subsample of spiders and flies was taken for Cd determination. It was demonstrated that a high cadmium assimilation (69.5\%) and an excretion rate approaching zero resulted in high Cd concentration factors. The results indicate the importance of spiders in cadmium biomagnification along critical pathways. (C) 2003 Elsevier Science (USA). All rights reserved.
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Fruits and seeds from the Tienen Formation at Dormaal, Palaeocene–Eocene transition in eastern Belgium
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New species of Macrocranion (Mammalia, Lipotyphla) from the earliest Eocene of North America and its biogeographic implications
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Report on the 2008 season of the Hierakonpolis expedition
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Fish as indicators of trade relationships in Roman times: the example of Sagalassos, Turkey
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