Are you what you eat? Effects of trophic discrimination factors on estimates of food assimilation and trophic position with a new estimation method

摘要: A key factor for estimates of assimilation resources and trophic position based on stable isotope data is the discrimination (TDF). TDFs are assumed literature reviews, but may vary depending a variety factors, including type diet. We analyzed effects alternative assimilated positions an omnivorous fish, Jenynsia multidentata, that reveals dietary variation among locations across salinity gradient coastal lagoon in southern Brazil. also compared foods ingested vs. assimilated. Food was estimated using carbon (δ13C) nitrogen (δ15N) ratios food sources consumer muscle tissue isotopic mixing model (SIAR); (TP) from production source δ15N values. Diet index relative importance frequency occurrence volumetric numeric proportions items stomach contents. The effect TDF TP tested three reported review papers. then created new method used source-specific (reported separately herbivores carnivores) weighted proportion to according estimate (hereafter TPWAR). found plant material not similar its diet fish at freshwater site, yielded best estimates. Animal made greatest contributions biomass irrespective model. produced consistent with differences along gradient. Our findings support idea should be studies omnivores, since improved our ability resource assimilation, two important ecological indicators.