Document Detail

Multiple sources of isotopic variation in a terrestrial arthropod community: challenges for disentangling food webs.
MedLine Citation:
PMID:  17716468     Owner:  NLM     Status:  MEDLINE    
Documenting trophic links in a food web has traditionally required complex exclusion experiments coupled with extraordinarily labor-intensive direct observations of predator foraging. Newer techniques such as stable isotope analysis (SIA) may facilitate relatively quick and accurate assessments of consumer feeding behavior. Ratios of N and C isotopes are thought to be useful for determining species' trophic position (e.g., 1 degrees consumer, 2 degrees consumer, or omnivore) and their original carbon source (e.g., C3 or C4 plants; terrestrial or marine nutrients). Thus far, however, applications of stable isotopes to terrestrial arthropod food webs have suggested that high taxon-specific variation may undermine the effectiveness of this method. We applied stable isotope analysis to a pear orchard food web, in which biological control of a dominant pest, pear psylla (Cacopsylla pyricola), involves primarily generalist arthropod predators with a high frequency of omnivory. We found multiple sources of isotopic variation in this food web, including differences among plant tissues; time, stage, and taxon-specific differences among herbivores (despite similar feeding modes); and high taxon-specific variation among predators (with no clear evidence of omnivory). Collectively, these multiple sources of isotopic variation blur our view of the structure of this food web. Idiosyncrasies in consumer trophic shifts make ad hoc application of SIA to even moderately complex food webs intractable. SIA may not be a generally applicable "quick and dirty" method for delineating terrestrial food web structure-not without calibration of specific consumer food trophic shifts.
Matthew P Daugherty; Cheryl J Briggs
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Environmental entomology     Volume:  36     ISSN:  0046-225X     ISO Abbreviation:  Environ. Entomol.     Publication Date:  2007 Aug 
Date Detail:
Created Date:  2007-08-24     Completed Date:  2007-10-10     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7502320     Medline TA:  Environ Entomol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  776-91     Citation Subset:  IM    
Department of Integrative Biology, University of California, Berkeley, CA 94720-3140, USA.
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MeSH Terms
Feeding Behavior / physiology
Food Chain*
Insects / physiology*
Plant Leaves
Pyrus / metabolism,  parasitology
Reg. No./Substance:

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