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Communication at the NABS Annual meeting, Keystone, 2000
(108) USING STABLE ISOTOPES TO COMPARE PRISTINE AND DISTURBED FOOD WEBS IN CUATRO CIENEGAS, MEXICO.
J.C. Marks1, B.A. Hungate1, and D.A. Hendrickson2. 1Department of Biology, Northern Arizona University, Flagstaff Arizona, USA 86011, 2Texas Natural History Collections, University of Texas, Austin, TX USA 78758-4445
Cuatro Cienegas, a protected area in northern Mexico, has over 200 freshwater habitats that host an unusual number of endemic fish and snails. The two major threats to the native species are water extraction and invading species. We used stable isotopes to compare food web structure in pristine versus disturbed habitats with particular focus on Cichlasoma minckleyi, an endemic cichlid, which is widespread in the basin and has a trophic polymorphisim. The two common morphs, (detritivore and molluscivore), differ in pharyngeal tooth morphology. Diet studies suggest strong overlap between the morphs. Stable isotopes offer two advantages over diet studies by allowing for large non-destructive samples and providing a temporally integrated assessment of diet. We collected fish from eight habitats and determined their tooth morphology and took a small fin clipping for isotope analysis. Morphs differed in δ13C, indicating that they have different food sources, but did not differ in d15N, suggesting that they occupy similar trophic positions. Hemichromis sp. an invading cichlid had similar δ15N values as C. minckleyi but differed in δ13C. Differences in isotope values among sites did not correlate with the Hemichromis invasion.
Presented at 11:45 AM on Tuesday, May 30, 2000 in Food Webs and Communities II
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