1,721,145 research outputs found
Testing the validity of functional response models using molecular gut content analysis for prey choice in soil predators
No full textUnveiling soil food web links: New PCR assays for detection of prey DNA in the gut of soil arthropod predators
No full textMolecular gut content analysis provides a highly specific and sensitive tool to examine the diet of soil invertebrates. Here, we present new polymerase chain reaction (PCR) assays for the detection of twelve prey taxa common in Central European forest soils. The assays target five species of collembolans as well as dipterans, gamasid and oribatid mites, lithobiid centipedes, spiders, staphylinid beetles and woodlice at the group level, amplifying 123-299 bp long DNA fragments. Cross-reactivity tests against 119 soil invertebrate taxa confirm their specificity. These new PCR assays were found to be highly sensitive, revealing the consumption of five different prey taxa in field-collected centipedes. Thus they provide a ready-to-use approach for unravelling trophic interactions among soil arthropods. (C) 2012 Elsevier Ltd. All rights reserved
Unveiling soil food web links: New PCR assays for detection of prey DNA in the gut of soil arthropod predators
No full textMolecular gut content analysis provides a highly specific and sensitive tool to examine the diet of soil invertebrates. Here, we present new polymerase chain reaction (PCR) assays for the detection of twelve prey taxa common in Central European forest soils. The assays target five species of collembolans as well as dipterans, gamasid and oribatid mites, lithobiid centipedes, spiders, staphylinid beetles and woodlice at the group level, amplifying 123-299 bp long DNA fragments. Cross-reactivity tests against 119 soil invertebrate taxa confirm their specificity. These new PCR assays were found to be highly sensitive, revealing the consumption of five different prey taxa in field-collected centipedes. Thus they provide a ready-to-use approach for unravelling trophic interactions among soil arthropods. (C) 2012 Elsevier Ltd. All rights reserved
Scavenging and active predation in generalist predators: A mesocosm study employing DNA-based gut content analysis
No full textScavenging presumably is common among invertebrate generalist predators, however, only few studies have specifically dealt with the consumption of dead prey. Here consumption of dead and living prey within a guild of generalist predators was investigated using mesocosm experiments and DNA-based gut content analysis. A community of predators including carabids, staphylinids and spiders was released into 0.2 m(2) mesocosms, planted with wheat and infested with grain aphids Sitobion avenae. At predator release, freshly killed bird cherry-oat aphids, Rhopalosiphum padi, were provided as carrion prey at the soil surface. Two days after predator release, predators were collected and their gut content screened for DNA of both aphid species using multiplex PCR.. Comparing detection frequencies of DNA from living and dead prey, we found that all predators frequently consumed dead aphids, except for the lycosid spider Trochosa ruricola which exclusively fed on S. avenae. In contrast, in the tetragnathid spicier Pachygnatha degeeri, supposed to feed mainly on living prey, detection rates of R. padi DNA were high. Our findings support previous assumptions that many generalist predators are facultative scavengers. This needs to be considered for the interpretation of field-derived data using approaches of gut content analyses as well as when assessing predators' pest control potential. (C) 2011 Elsevier GmbH. All rights reserved.German Research Foundation (DFG) [SCHE 376/14
Evaluation of three molecular markers for identification of European primary parasitoids of cereal aphids and their hyperparasitoids.
No full textAphids are major pests of cereal crops and a suite of hymenopteran primary parasitoids play an important role in regulating their populations. However, hyperparasitoids may disrupt the biocontrol services provided by primary parasitoids. As such, understanding cereal aphid-primary parasitoid-hyperparasitoid interactions is vital for a reliable parasitoid-based control of cereal aphids. For this, the ability to identify the different primary and hyperparasitoid species is necessary. Unfortunately, this is often difficult due to a lack of morphologically diagnostic features. DNA sequence-based species identification of parasitoids can overcome these hurdles. However, comprehensive DNA sequence information is lacking for many of these groups, particularly for hyperparasitoids. Here we evaluate three genes [cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S) and 18S ribosomal RNA (18S)] for their suitability to identify 24 species of primary parasitoids and 16 species of hyperparasitoids associated with European cereal aphids. To identify aphelinid primary parasitoid species and hyperparasitoids, we found 16S to be more suitable compared to COI sequences. In contrast, the Aphidiinae are best identified using COI due to better species-level resolution and a more comprehensive DNA sequence database compared to 16S. The 18S gene was better suited for group-specific identification of parasitoids, but did not provide resolution at the species level. Our results provide a DNA sequence database for cereal aphid primary parasitoids and their associated hyperparasitoids in Central Europe, which will allow further improvement of our understanding of cereal aphid-primary parasitoid-hyperparasitoid interactions in relation to aphid biological control
Dwarf shrub litter as a food source for macro-decomposers in alpine pastureland
No full textDwarf shrub litter is thought to be of poor quality and palatability for macro-decomposers. In laboratory feeding experiments, however, it was found that this litter type represents a potential food source for earthworms and millipedes. Here we tested whether this is true under natural conditions by conducting a 1 year field experiment on an abandoned alpine pasture in Tyrol (Austria). As the natural isotopic signatures of plant litter do not allow discriminating between different plant species, dwarf shrub litter, artificially enriched in N-15, was offered in experimental plots to the macro-decomposer community. Both the earthworm Lumbricus rubellus and the millipede Cylindrojulus fulviceps fed on dwarf shrub litter as indicated by their increased delta N-15 signatures, but IsoError analysis indicated a clear preference for grass litter for all macro-decomposer species investigated. Soil delta N-15 signatures were only marginally affected by the experimental provision of N-15-enriched dwarf shrub litter, whereas litter from other, unlabelled, plants became enriched by the isotopic tracer to some extent. Except for one grass species, plants harvested at the end of the experiment were not enriched in N-15, suggesting that the N-uptake from decomposing litter material by plants on abandoned alpine pastureland is slow. (C) 2008 Elsevier B.V. All rights reserved.Austrian Science Fund [P 16027, P 18520
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Testing the validity of functional response models using molecular gut content analysis for prey choice in soil predators
No full textAnalysis of predator–prey interactions is a core concept of animal ecology, explaining structure and dynamics of animal food webs. Measuring the functional response, i.e. the intake rate of a consumer as a function of prey density, is a powerful method to predict the strength of trophic links and assess motives of prey choice, particularly in arthropod communities. However, due to their reductionist set‐up, functional responses, which are based on laboratory feeding experiments, may not display field conditions, possibly leading to skewed results. Here, we tested the validity of functional responses of centipede predators and their prey by comparing them with empirical gut content data from field‐collected predators. Our predator–prey system included lithobiid and geophilomorph centipedes, abundant and widespread predators of forest soils and their soil‐dwelling prey. First, we calculated the body size‐dependent functional responses of centipedes using a published functional response model in which we included natural prey abundances and animal body masses. This allowed us to calculate relative proportions of specific prey taxa in the centipede diet. In a second step, we screened field‐collected centipedes for DNA of eight abundant soil‐living prey taxa and estimated their body size‐dependent proportion of feeding events. We subsequently compared empirical data for each of the eight prey taxa, on proportional feeding events with functional response‐derived data on prey proportions expected in the gut, showing that both approaches significantly correlate in five out of eight predator–prey links for lithobiid centipedes but only in one case for geophilomorph centipedes. Our findings suggest that purely allometric functional response models, which are based on predator–prey body size ratios are too simple to explain predator–prey interactions in a complex system such as soil. We therefore stress that specific prey traits, such as defence mechanisms, must be considered for accurate predictions.DFG Priority Program 1374 “Infrastructure-Biodiversity-Exploratories”German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-LeipzigGerman Research Foundation http://dx.doi.org/10.13039/50110000165
Structural and functional characteristics of high alpine soil macro-invertebrate communities
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