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Isotopic fractionation in a large herbivorous insect, the Auckland tree weta.
MedLine Citation:
PMID:  20709068     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
Determining diet and trophic position of species with stable isotopes requires appropriate trophic enrichment estimates between an animal and its potential foods. These estimates are particularly important for cryptic foragers where there is little comparative dietary information. Nonetheless, many trophic enrichment estimates are based on related taxa, without confirmation of accuracy using laboratory trials. We used stable isotope analysis to investigate diet and to resolve trophic relationships in a large endemic insect, the Auckland tree weta (Hemideina thoracica White). Comparisons of isotopes in plant foods fed to captive wetas with isotope ratios in their frass provided variable results, so frass isotope values had limited usefulness as a proxy indicator of trophic level. Isotopic values varied between different tissues, with trophic depletion of (15)N highest in body fat and testes. Tissue fractionation was consistent in captive and wild caught wetas, and isotopic values were not significantly different between the two groups, suggesting that this weta species is primarily herbivorous. Whole-body values in captive wetas demonstrated trophic depletion (Δδ) for δ(15)N of about -0.77 ‰ and trophic enrichment of 4.28 ‰ for δ(13)C. These values differ from commonly estimated trophic enrichments for both insects and herbivores and indicate the importance of laboratory trials to determine trophic enrichment. Isotopic values for femur muscles from a number of local wild weta populations did not vary consistently with body weight or size, suggesting that juveniles eat the same foods as adults. Considerable variation among individuals within and between populations suggests that isotopic values are strongly influenced by food availability and individual foraging traits.
Authors:
Priscilla M Wehi; Brendan J Hicks
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2010-08-20
Journal Detail:
Title:  Journal of insect physiology     Volume:  56     ISSN:  1879-1611     ISO Abbreviation:  J. Insect Physiol.     Publication Date:  2010 Dec 
Date Detail:
Created Date:  2010-10-29     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985080R     Medline TA:  J Insect Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1877-82     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier Ltd. All rights reserved.
Affiliation:
Centre for Biodiversity and Ecology Research, Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand. p.m.mcallum@massey.ac.nz
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