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Predator hunting mode influences patterns of prey use from grazing and epigeic food webs.
MedLine Citation:
PMID:  22926724     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Multichannel omnivory by generalist predators, especially the use of both grazing and epigeic prey, has the potential to increase predator abundance and decrease herbivore populations. However, predator use of the epigeic web (soil surface detritus/microbe/algae consumers) varies considerably for reasons that are poorly understood. We therefore used a stable isotope approach to determine whether prey availability and predator hunting style (active hunting vs. passive web-building) impacted the degree of multichannel omnivory by the two most abundant predators on an intertidal salt marsh, both spiders. We found that carbon isotopic values of herbivores remained constant during the growing season, while values for epigeic feeders became dramatically more enriched such that values for the two webs converged in August. Carbon isotopic values for both spider species remained midway between the two webs as values for epigeic feeders shifted, indicating substantial use of prey from both food webs by both spider species. As the season progressed, prey abundance in the grazing food web increased while prey abundance in the epigeic web remained constant or declined. In response, prey consumption by the web-building spider shifted toward the grazing web to a much greater extent than did consumption by the hunting spider, possibly because passive web-capture is more responsive to changes in prey availability. Although both generalist predator species engaged in multichannel omnivory, hunting mode influenced the extent to which these predators used prey from the grazing and epigeic food webs, and could thereby influence the strength of trophic cascades in both food webs.
Authors:
Gina M Wimp; Shannon M Murphy; Danny Lewis; Margaret R Douglas; Ramya Ambikapathi; Lie'ann Van-Tull; Claudio Gratton; Robert F Denno
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-8-25
Journal Detail:
Title:  Oecologia     Volume:  -     ISSN:  1432-1939     ISO Abbreviation:  Oecologia     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-8-28     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Biology Department, Georgetown University, Washington, DC, 20057, USA, gmw22@georgetown.edu.
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