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High intraspecific variability in carbon and nitrogen stable isotope ratios of lake chironomid larvae
Author(s) -
Grey Jonathan,
Kelly Andrew,
Jones Roger I.
Publication year - 2004
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2004.49.1.0239
Subject(s) - intraspecific competition , trophic level , biology , benthic zone , chironomidae , food web , ecology , chironomus , δ13c , stable isotope ratio , larva , physics , quantum mechanics
Stable isotope analyses of chironomid trophic interactions have recently indicated the potential importance of isotopically light biogenic methane as a carbon source. Mass balance of isotope ratios suggests that small proportional differences in ingestion of such an isotopically distinct basal resource by individual consumers can result in considerable intraspecific variability. To test this, we collected individual larvae of two closely related chironomid species ( Chironomus anthracinus and Chironomus plumosus ) from six lakes and analyzed their δ 13 C and δ 15 N. Intraspecific variability in larval δ 13 C and δ 15 N values was greater in lakes where chironomids were more 13 C depleted. C. plumosus exhibited higher intraspecific variability relative to C. anthracinus . In two lakes, individual C. plumosus exhibited a range of 35‰ for δ 13 C and 16‰ for δ 15 N (equivalent to five trophic levels). There was a strong positive relationship between larval δ 13 C and δ 15 N, both between individuals from the same lake and also between lakes, suggesting that the underlying causative mechanisms are similar. Furthermore, larvae from deeper sites, which are more susceptible to prolonged anoxia, exhibited greater intraspecific variability, and larger larvae were significantly 13 C depleted. Such high intraspecific variability can confound the interpretation of benthic food web stable isotope values. We advocate the reporting of more intraspecific isotopic variability as a means to further examine niche breadth and feeding behavior.