A general hypothesis‐testing framework for stable isotope ratios in ecological studies

Turner, Thomas F.; Collyer, Michael L.; Krabbenhoft, Trevor J.

doi:10.1890/09-1454.1

Cited by 197 publications

(206 citation statements)

References 23 publications

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“…Overall, there were 386 juvenile Chinook salmon that fitted our operational definition for equilibrium, with sample size of equilibrated juvenile Chinook sal mon ranging from 7 in CA to 144 in SEAK (Table S1). Due to low sample sizes of equilibrated N space, we tested for differences in isotopic niche position among regions using the residual permutation procedures outlined in Turner et al (2010). This method is based on Euclidean distance measures of each individual's position in bivariate δ 13 C−δ 15 N space (Turner et al 2010).…”

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confidence: 99%

“…Due to low sample sizes of equilibrated N space, we tested for differences in isotopic niche position among regions using the residual permutation procedures outlined in Turner et al (2010). This method is based on Euclidean distance measures of each individual's position in bivariate δ 13 C−δ 15 N space (Turner et al 2010). We ran the procedure for 1000 iterations.…”

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Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean

Hertz¹,

Trudel²,

Brodeur³

et al. 2015

Mar. Ecol. Prog. Ser.

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Trophic interactions within and among species vary widely across spatial scales and species' ontogeny. However, the drivers and implications of this variability are not well understood. Juvenile Chinook salmon Oncorhynchus tshawytscha have a wide distribution, ranging from northern California to the eastern Bering Sea in North America, but it is largely unknown how their feeding ecology varies and changes with ontogeny across this range. We collected juvenile Chinook salmon and zooplankton using standardized protocols along the coastal Northeast Pacific Ocean. Using a combination of stomach contents and stable isotopes of nitrogen (δ 15 N) and carbon (δ 13 C) to characterize feeding ecology, we found regional differences in prey utilization by juvenile Chinook salmon. With growth and ontogeny, juvenile salmon in all regions became equilibrated with oceanic isotopic values. There were regional differences in the δ 13 C values of juvenile Chinook salmon that may correspond to regional differences in sea surface temperature. There were also regional differences in stable isotope-derived trophic level, and these estimates differed from those derived from stomach contents, possibly due to the different periods over which these metrics integrate. Dietary niche width, as indicated by stable isotopes, corresponded to the expected dietary diversity from stomach contents, combined with the isotopic variability seen in baseline values. Our results indicate strong geographic and ontogenetic differences in feeding ecology of juvenile Chinook salmon. These differences are likely influenced by a combination of ocean-entry date, ocean-entry size, ontogeny, growth rates and regional conditions.

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confidence: 99%

mentioning

confidence: 99%

Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean

Hertz¹,

Trudel²,

Brodeur³

et al. 2015

Mar. Ecol. Prog. Ser.

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“…We generated null distributions from residual permutation procedures to test for differences in these two metrics among species, and we considered them significantly different if the difference did not overlap zero (Turner et al 2010). …”

Section: Interspecific Isotopic Niche Variationmentioning

confidence: 99%

Different prey resources suggest little competition between non-native frogs and insectivorous birds despite isotopic niche overlap

Smith

Beard

Shiels³

2016

Biol Invasions

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Non-native amphibians often compete with native amphibians in their introduced range, but their competitive effects on other vertebrates are less well known. The Puerto Rican coqui frog (Eleutherodactylus coqui) has colonized the island of Hawaii, and has been hypothesized to compete with insectivorous birds and bats. To address if the coqui could compete with these vertebrates, we used stable isotope analyses to compare the trophic position and isotopic niche overlap between the coqui, three insectivorous bird species, and the Hawaiian hoary bat. Coquis shared similar trophic position to Hawaii amakihi, Japanese white-eye, and red-billed leiothrix. Coquis were about 3 % less enriched in d 15 N than the Hawaiian hoary bat, suggesting the bats feed at a higher trophic level than coquis. Analyses of potential diet sources between coquis and each of the three bird species indicate that there was more dietary overlap between bird species than any of the birds and the coqui. Results suggest that Acari, Amphipoda, and Blattodea made up[90% of coqui diet, while Araneae made up only 2% of coqui diet, but approximately 25% of amakihi and white-eye diet. The three bird species shared similar proportions of Lepidoptera larvae, which were *25% of their diet. Results suggest that coquis share few food resources with insectivorous birds, but occupy a similar trophic position, which could indicate weak competition. However, resource competition may not be the only way coquis impact insectivorous birds, and future research should examine whether coqui invasions are associated with changes in bird abundance.

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“…The isotopic niche is often visualised as bivariate plots of mean δ 13 C and δ 15 N values and variance estimates (Bearhop et al 2004). Statistical methods examining the dispersion of stable isotope values in xy-space (Layman et al 2007a, Turner et al 2010 include convex hull (Layman et al 2007a) and standard ellipse area (SEA) ; these aim to define a species' trophic niche in isotopic-space with each data point representing an individual's use of resources and habitat (Layman et al 2012). …”

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confidence: 99%

“…The parameters used to calculate and plot the SEA include: the lengths of the semi-major (a) and semi-minor (b) axes of the SEA; the angle in radians (θ) between a and the x-axis; the eccentricity (E) of the standard ellipse between 0 < E < 1, where E = 0 is a perfect circle and E → 1 indicates the standard ellipse becomes more elongated . Turner et al (2010) originally proposed the use of E as a measure of isotopic variability. However, E and θ have not been reported to date in relation to SEA and may help inform its ecological interpretation.…”

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confidence: 99%

Isotopic niche variability in macroconsumers of the East Scotia Ridge (Southern Ocean) hydrothermal vents: What more can we learn from an ellipse?

Reid¹,

Sweeting²,

Wigham³

et al. 2016

Mar. Ecol. Prog. Ser.

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Aspects of between-individual trophic niche width can be explored through the isotopic niche concept. In many cases isotopic variability can be influenced by the scale of sampling and biological characteristics including body size or sex. Sample size-corrected (SEAc) and Bayesian (SEAb) standard ellipse areas and generalised least squares (GLS) models were used to explore the spatial variability of δ 13 C and δ 15 N in Kiwa tyleri (decapod), Gigantopelta chessoia (peltospirid gastropod) and Vulcanolepas scotiaensis (stalked barnacle) collected from 3 hydrothermal vent field sites (E2, E9N and E9S) on the East Scotia Ridge (ESR), Southern Ocean. SEAb only revealed spatial differences in isotopic niche area in male K. tyleri. However, the parameters used to draw the SEAc, eccentricity (E) and angle of the major SEAc axis to the x-axis (θ), indicated spatial differences in the relationships between δ 13 C and δ 15 N in all 3 species. The GLS models indicated that there were spatial differences in isotope−length trends, which were related to E and θ of the SEAc. This indicated that E and θ were potentially driven by underlying trophic and biological processes that varied with body size. Examination of the isotopic niches using standard ellipse areas and their parameters in conjunction with length-based analyses provided a means by which a proportion of the isotopic variability within each species could be described. We suggest that the parameters E and θ offer additional ecological insight that has so far been overlooked in isotopic niche studies.

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A general hypothesis‐testing framework for stable isotope ratios in ecological studies

Cited by 197 publications

References 23 publications

Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean

Continental-scale variability in the feeding ecology of juvenile Chinook salmon along the coastal Northeast Pacific Ocean

Different prey resources suggest little competition between non-native frogs and insectivorous birds despite isotopic niche overlap

Isotopic niche variability in macroconsumers of the East Scotia Ridge (Southern Ocean) hydrothermal vents: What more can we learn from an ellipse?

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