Nematode Communities (nematode + community)

Distribution by Scientific Domains


Selected Abstracts


Influence of 4-nonylphenol on the structure of nematode communities in freshwater microcosms

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2004
Sebastian Höss
Abstract We investigated the effect of 4-nonylphenol (NP) on nematode communities in the sediment of freshwater microcosms. Seven treatments were dosed with various concentrations of NP over a period of six weeks by using a controlled-release method (NP1-NP7; maximum sediment concentrations: 0.29,3.37 mg/kg dry wt). Four microcosms were not exposed to NP and served as controls. Nematode communities were analyzed over a period of 15 weeks, including sampling dates before, within, and after the NP application. Communities were characterized in terms of total nematode abundance and species diversity (Shannon index and evenness), as well as composition of species, feeding types, and different life-history strategists (maturity index [MI]). Species composition was analyzed by using a multivariate method (principal response curves). Total nematode abundance and species diversity were not affected in any of the NP-treated microcosms. However, in the highest dosed treatment, NP-induced changes in the nematode communities occurred. Species and feeding types composition, as well as the MI, were affected in the postapplication period, with species composition being altered most clearly. In the highest dosed treatment, deposit-feeding species, classified as colonizers (Eumonhystera), increased in dominance, whereas epistrate feeders and chewers (Prodesmodora and Tobrilus) decreased in relative abundance compared to the control. [source]


Field evidence for indirect interactions between foliar-feeding insect and root-feeding nematode communities on Nicotiana tabacum

ECOLOGICAL ENTOMOLOGY, Issue 2 2009
IAN KAPLAN
Abstract 1.,As herbivory often elicits systemic changes in plant traits, indirect interactions via induced plant responses may be a pervasive feature structuring herbivore communities. Although the importance of this phenomenon has been emphasised for herbivorous insects, it is unknown if and how induced responses contribute to the organisation of other major phytoparasitic taxa. 2.,Survey and experimental field studies were used to investigate the role of plants in linking the dynamics of foliar-feeding insects and root-feeding nematodes on tobacco, Nicotiana tabacum. 3.,Plant-mediated interactions between insects and nematodes could largely be differentiated by insect feeding guild, with positive insect,nematode interactions predominating with leaf-chewing insects (caterpillars) and negative interactions occurring with sap-feeding insects (aphids). For example, insect defoliation was positively correlated with the abundance of root-feeding nematodes, but aphids and nematodes were negatively correlated. Experimental field manipulations of foliar insect and nematode root herbivory also tended to support this outcome. 4.,Overall, these results suggest that plants indirectly link the dynamics of divergent consumer taxa in spatially distinct ecosystems. This lends support to the growing perception that plants play a critical role in propagating indirect effects among a diverse assemblage of consumers. [source]


Influence of 4-nonylphenol on the structure of nematode communities in freshwater microcosms

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2004
Sebastian Höss
Abstract We investigated the effect of 4-nonylphenol (NP) on nematode communities in the sediment of freshwater microcosms. Seven treatments were dosed with various concentrations of NP over a period of six weeks by using a controlled-release method (NP1-NP7; maximum sediment concentrations: 0.29,3.37 mg/kg dry wt). Four microcosms were not exposed to NP and served as controls. Nematode communities were analyzed over a period of 15 weeks, including sampling dates before, within, and after the NP application. Communities were characterized in terms of total nematode abundance and species diversity (Shannon index and evenness), as well as composition of species, feeding types, and different life-history strategists (maturity index [MI]). Species composition was analyzed by using a multivariate method (principal response curves). Total nematode abundance and species diversity were not affected in any of the NP-treated microcosms. However, in the highest dosed treatment, NP-induced changes in the nematode communities occurred. Species and feeding types composition, as well as the MI, were affected in the postapplication period, with species composition being altered most clearly. In the highest dosed treatment, deposit-feeding species, classified as colonizers (Eumonhystera), increased in dominance, whereas epistrate feeders and chewers (Prodesmodora and Tobrilus) decreased in relative abundance compared to the control. [source]


Impact of elevated carbon dioxide on the rhizosphere communities of Carex arenaria and Festuca rubra

GLOBAL CHANGE BIOLOGY, Issue 11 2007
BARBARA DRIGO
Abstract The increase in atmospheric carbon dioxide (CO2) levels is predicted to stimulate plant carbon (C) fixation, potentially influencing the size, structure and function of micro- and mesofaunal communities inhabiting the rhizosphere. To assess the effects of increased atmospheric CO2 on bacterial, fungal and nematode communities in the rhizosphere, Carex arenaria (a nonmycorrhizal plant species) and Festuca rubra (a mycorrhizal plant species) were grown in three dune soils under controlled soil temperature and moisture conditions, while subjecting the aboveground compartment to defined atmospheric conditions differing in CO2 concentrations (350 and 700 ,L L,1). Real-time polymerase chain reaction (PCR) and PCR-denaturing gradient gel electrophoresis methods were used to examine effects on the size and structure of rhizosphere communities. Multivariate analysis of community profiles showed that bacteria were most affected by elevated CO2, and fungi and nematodes to a lesser extent. The influence of elevated CO2 was plant dependent, with the mycorrhizal plant (F. rubra) exerting a greater influence on bacterial and fungal communities. Biomarker data indicated that arbuscular mycorrhizal fungi (AMF) may play an important role in the observed soil community responses. Effects of elevated CO2 were also soil dependent, with greater influence observed in the more organic-rich soils, which also supported higher levels of AMF colonization. These results indicate that responses of soil-borne communities to elevated CO2 are different for bacteria, fungi and nematodes and dependent on the plant type and soil nutrient availability. [source]


Evaluating high-throughput sequencing as a method for metagenomic analysis of nematode diversity

MOLECULAR ECOLOGY RESOURCES, Issue 6 2009
DOROTA L. PORAZINSKA
Abstract Nematodes play an important role in ecosystem processes, yet the relevance of nematode species diversity to ecology is unknown. Because nematode identification of all individuals at the species level using standard techniques is difficult and time-consuming, nematode communities are not resolved down to the species level, leaving ecological analysis ambiguous. We assessed the suitability of massively parallel sequencing for analysis of nematode diversity from metagenomic samples. We set up four artificial metagenomic samples involving 41 diverse reference nematodes in known abundances. Two samples came from pooling polymerase chain reaction products amplified from single nematode species. Two additional metagenomic samples consisted of amplified products of DNA extracted from pooled nematode species. Amplified products involved two rapidly evolving ~400-bp sections coding for the small and large subunit of rRNA. The total number of reads ranged from 4159 to 14771 per metagenomic sample. Of these, 82% were > 199 bp in length. Among the reads > 199 bp, 86% matched the referenced species with less than three nucleotide differences from a reference sequence. Although neither rDNA section recovered all nematode species, the use of both loci improved the detection level of nematode species from 90 to 97%. Overall, results support the suitability of massively parallel sequencing for identification of nematodes. In contrast, the frequency of reads representing individual species did not correlate with the number of individuals in the metagenomic samples, suggesting that further methodological work is necessary before it will be justified for inferring the relative abundances of species within a nematode community. [source]


Above- and belowground insect herbivores differentially affect soil nematode communities in species-rich plant communities

OIKOS, Issue 6 2007
Gerlinde B. De Deyn
Interactions between above- and belowground invertebrate herbivores alter plant diversity, however, little is known on how these effects may influence higher trophic level organisms belowground. Here we explore whether above- and belowground invertebrate herbivores which alter plant community diversity and biomass, in turn affect soil nematode communities. We test the hypotheses that insect herbivores 1) alter soil nematode diversity, 2) stimulate bacterial-feeding and 3) reduce plant-feeding nematode abundances. In a full factorial outdoor mesocosm experiment we introduced grasshoppers (aboveground herbivores), wireworms (belowground herbivores) and a diverse soil nematode community to species-rich model plant communities. After two years, insect herbivore effects on nematode diversity and on abundance of herbivorous, bacterivorous, fungivorous and omni-carnivorous nematodes were evaluated in relation to plant community composition. Wireworms did not affect nematode diversity despite enhanced plant diversity, while grasshoppers, which did not affect plant diversity, reduced nematode diversity. Although grasshoppers and wireworms caused contrasting shifts in plant species dominance, they did not affect abundances of decomposer nematodes at any trophic level. Primary consumer nematodes were, however, strongly promoted by wireworms, while community root biomass was not altered by the insect herbivores. Overall, interaction effects of wireworms and grasshoppers on the soil nematodes were not observed, and we found no support for bottom-up control of the nematodes. However, our results show that above- and belowground insect herbivores may facilitate root-feeding rather than decomposer nematodes and that this facilitation appears to be driven by shifts in plant species composition. Moreover, the addition of nematodes strongly suppressed shoot biomass of several forb species and reduced grasshopper abundance. Thus, our results suggest that nematode feedback effects on plant community composition, due to plant and herbivore parasitism, may strongly depend on the presence of insect herbivores. [source]


Decline in a dominant invertebrate species contributes to altered carbon cycling in a low-diversity soil ecosystem

GLOBAL CHANGE BIOLOGY, Issue 8 2008
J. E. BARRETT
Abstract Low-diversity ecosystems cover large portions of the Earth's land surface, yet studies of climate change on ecosystem functioning typically focus on temperate ecosystems, where diversity is high and the effects of individual species on ecosystem functioning are difficult to determine. We show that a climate-induced decline of an invertebrate species in a low-diversity ecosystem could contribute to significant changes in carbon (C) cycling. Recent climate variability in the McMurdo Dry Valleys of Antarctica is associated with changes in hydrology, biological productivity, and community composition of terrestrial and aquatic ecosystems. One of the greatest changes documented in the dry valleys is a 65% decrease in the abundance of the dominant soil invertebrate (Scottnema lindsayae, Nematoda) between 1993 and 2005, illustrating sensitivity of biota in this ecosystem to small changes in temperature. Globally, such declines are expected to have significant influences over ecosystem processes such as C cycling. To determine the implications of this climate-induced decline in nematode abundance on soil C cycling we followed the fate of a 13C tracer added to soils in Taylor Valley, Antarctica. Carbon assimilation by the dry valley nematode community contributed significantly to soil C cycling (2,7% of the heterotrophic C flux). Thus, the influence of a climate-induced decline in abundance of a dominant species may have a significant effect on ecosystem functioning in a low-diversity ecosystem. [source]


Evaluating high-throughput sequencing as a method for metagenomic analysis of nematode diversity

MOLECULAR ECOLOGY RESOURCES, Issue 6 2009
DOROTA L. PORAZINSKA
Abstract Nematodes play an important role in ecosystem processes, yet the relevance of nematode species diversity to ecology is unknown. Because nematode identification of all individuals at the species level using standard techniques is difficult and time-consuming, nematode communities are not resolved down to the species level, leaving ecological analysis ambiguous. We assessed the suitability of massively parallel sequencing for analysis of nematode diversity from metagenomic samples. We set up four artificial metagenomic samples involving 41 diverse reference nematodes in known abundances. Two samples came from pooling polymerase chain reaction products amplified from single nematode species. Two additional metagenomic samples consisted of amplified products of DNA extracted from pooled nematode species. Amplified products involved two rapidly evolving ~400-bp sections coding for the small and large subunit of rRNA. The total number of reads ranged from 4159 to 14771 per metagenomic sample. Of these, 82% were > 199 bp in length. Among the reads > 199 bp, 86% matched the referenced species with less than three nucleotide differences from a reference sequence. Although neither rDNA section recovered all nematode species, the use of both loci improved the detection level of nematode species from 90 to 97%. Overall, results support the suitability of massively parallel sequencing for identification of nematodes. In contrast, the frequency of reads representing individual species did not correlate with the number of individuals in the metagenomic samples, suggesting that further methodological work is necessary before it will be justified for inferring the relative abundances of species within a nematode community. [source]


Above- and belowground insect herbivores differentially affect soil nematode communities in species-rich plant communities

OIKOS, Issue 6 2007
Gerlinde B. De Deyn
Interactions between above- and belowground invertebrate herbivores alter plant diversity, however, little is known on how these effects may influence higher trophic level organisms belowground. Here we explore whether above- and belowground invertebrate herbivores which alter plant community diversity and biomass, in turn affect soil nematode communities. We test the hypotheses that insect herbivores 1) alter soil nematode diversity, 2) stimulate bacterial-feeding and 3) reduce plant-feeding nematode abundances. In a full factorial outdoor mesocosm experiment we introduced grasshoppers (aboveground herbivores), wireworms (belowground herbivores) and a diverse soil nematode community to species-rich model plant communities. After two years, insect herbivore effects on nematode diversity and on abundance of herbivorous, bacterivorous, fungivorous and omni-carnivorous nematodes were evaluated in relation to plant community composition. Wireworms did not affect nematode diversity despite enhanced plant diversity, while grasshoppers, which did not affect plant diversity, reduced nematode diversity. Although grasshoppers and wireworms caused contrasting shifts in plant species dominance, they did not affect abundances of decomposer nematodes at any trophic level. Primary consumer nematodes were, however, strongly promoted by wireworms, while community root biomass was not altered by the insect herbivores. Overall, interaction effects of wireworms and grasshoppers on the soil nematodes were not observed, and we found no support for bottom-up control of the nematodes. However, our results show that above- and belowground insect herbivores may facilitate root-feeding rather than decomposer nematodes and that this facilitation appears to be driven by shifts in plant species composition. Moreover, the addition of nematodes strongly suppressed shoot biomass of several forb species and reduced grasshopper abundance. Thus, our results suggest that nematode feedback effects on plant community composition, due to plant and herbivore parasitism, may strongly depend on the presence of insect herbivores. [source]