DOI: 10.5061/dryad.tht76hdw8
title: Data from: The effects of lipid extraction on δ13C and δ15N values and use of lipid-correction models across tissues, taxa, and trophic groups

description: Lipid-rich animal tissues have low δ13C values, which can lead to
 inaccurate ecological inferences. Chemical lipid extraction (LE) or
 correction models account for this depletion, but the need for LE or
 correction is tissue- and species-specific. Also, LE can
 alter δ15N values, increasing labor and costs because bulk
 samples must be analyzed for δ15N values separately. We
 studied the effects of LE on δ13C and δ15N values in
 liver, muscle, and skin of common bottlenose dolphins (Tursiops truncatus)
 and West Indian manatees (Trichechus manatus), two ecologically important
 species that occupy different trophic levels. We fit lipid-correction
 models to each species. We also performed a meta-analysis to more broadly
 determine the effects of LE across taxa, tissues, and trophic groups
 (carnivores, omnivores, and herbivores) and to fit lipid-correction models
 to different taxonomic and trophic groups. Lipid extraction
 increased the δ13C values in dolphin tissues but had little
 effect on manatee tissues and no effect on the δ15N values in
 either species. A mass-balance lipid-correction model best fit the data
 from all dolphin tissues, and a linear model best fit data for manatee
 liver while null models best fit data from manatee muscle and skin. Across
 128 terrestrial and aquatic species, the effects of LE varied among
 tissues and were lower for herbivores compared to carnivores. The
 best-fitting lipid-correction models varied among tissue, taxa, and
 trophic groups. Finally, the δ15N values from muscle and liver
 were affected by lipid extraction. Our results strengthen the
 growing body of evidence that the need for LE is tissue- and
 species-specific, without a reliable C:N ratio predictive threshold. The
 prediction errors of lipid-correction models generally decreased with
 taxonomic- and trophic-specificity. The smaller effects of LE in
 herbivores may be due to differences in diet composition or the physiology
 of lipid synthesis in members of this trophic group. These results suggest
 researchers should use the most species-, tissue-, and trophic-group
 specific information on LE available and, if not available, perform LE on
 a subset of samples prior to analysis to determine effects.
description: This file contains three sheets. The first sheet, titled <i>read.me, </i>contains column title information for the second and third sheets. The second sheet contains data on stable carbon and nitrogen values of bulk and lipid-extracted samples from liver, skin, and muscle of common bottlenose dolphins (<i>Tursiops truncatus</i>) and West Indian manatees (<i>Trichechus manatus</i>). For this sheet, each row contains the sample and animal ID, tissue type, species, bulk and lipid extracted stable carbon and nitrogen values, and carbon:nitrogen (CN) ratios, as well as the difference between the bulk and lipid-extracted stable carbon and nitrogen values and CN ratios. The third sheet contains meta-analysis data that was obtained from the literature. For this sheet, each row represents a species and contains information on the taxonomic and trophic groups as well as data on the differences between bulk and lipid-extracted liver, muscle, and skin samples as well as bulk CN ratio for each tissue type and the reported instrumental error.