Document Detail

Intraguild interactions between spiders and ants and top-down control in a grassland food web.
MedLine Citation:
PMID:  17091284     Owner:  NLM     Status:  MEDLINE    
In most terrestrial ecosystems ants (Formicidae) as eusocial insects and spiders (Araneida) as solitary trappers and hunters are key predators. To study the role of predation by these generalist predators in a dry grassland, we manipulated densities of ants and spiders (natural and low density) in a two-factorial field experiment using fenced plots. The experiment revealed strong intraguild interactions between ants and spiders. Higher densities of ants negatively affected the abundance and biomass of web-building spiders. The density of Linyphiidae was threefold higher in plots without ant colonies. The abundance of Formica cunicularia workers was significantly higher in spider-removal plots. Also, population size of springtails (Collembola) was negatively affected by the presence of wandering spiders. Ants reduced the density of Lepidoptera larvae. In contrast, the abundance of coccids (Ortheziidae) was positively correlated with densities of ants. To gain a better understanding of the position of spiders, ants and other dominant invertebrate groups in the studied food web and important trophic links, we used a stable isotope analysis ((15)N and (13)C). Adult wandering spiders were more enriched in (15)N relative to (14)N than juveniles, indicating a shift to predatory prey groups. Juvenile wandering and web-building spiders showed delta(15)N ratios just one trophic level above those of Collembola, and they had similar delta(13)C values, indicating that Collembola are an important prey group for ground living spiders. The effects of spiders demonstrated in the field experiment support this result. We conclude that the food resource of spiders in our study system is largely based on the detrital food web and that their effects on herbivores are weak. The effects of ants are not clear-cut and include predation as well as mutualism with herbivores. Within this diverse predator guild, intraguild interactions are important structuring forces.
Dirk Sanders; Christian Platner
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2006-11-08
Journal Detail:
Title:  Oecologia     Volume:  150     ISSN:  0029-8549     ISO Abbreviation:  Oecologia     Publication Date:  2007 Jan 
Date Detail:
Created Date:  2006-12-20     Completed Date:  2007-04-12     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  611-24     Citation Subset:  IM    
Ecology Group, Institute of Zoology, Anthropology and Developmental Biology, Georg-August University of Göttingen, Berliner Str. 28, 37073, Gottingen, Germany.
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MeSH Terms
Ants / physiology*
Arthropods / classification,  physiology*
Carbon Isotopes / analysis
Food Chain*
Nitrogen Isotopes / analysis
Plants / classification
Population Density
Population Dynamics
Predatory Behavior
Spiders / physiology*
Reg. No./Substance:
0/Carbon Isotopes; 0/Nitrogen Isotopes

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