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Beyond carbon and nitrogen: guidelines for estimating three-dimensional isotopic niche space.

Rossman S, Ostrom PH, Gordon F, Zipkin EF - Ecol Evol (2016)

Bottom Line: Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use.We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling.Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative BiologyMichigan State UniversityEast LansingMichigan48824; Ecology Evolutionary Biology and Behavior ProgramMichigan State UniversityEast LansingMichigan48824; Hubbs-Sea World Research Institute3830 S. Highway A1A #4-181Melbourne BeachFlorida32951.

ABSTRACT
Isotopic niche has typically been characterized through carbon and nitrogen ratios and most modeling approaches are limited to two dimensions. Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use. The ellipse niche model was recently generalized to n-dimensions. We present an analogous methodology which incorporates variation across three stable dimensions to estimate the significant features of a population's isotopic niche space including: 1) niche volume (referred to as standard ellipsoid volume, SEV), 2) relative centroid location (CL), 3) shape and 4) area of overlap between multiple ellipsoids and 5) distance between two CLs. We conducted a simulation study showing the accuracy and precision of three dimensional niche models across a range of values. Importantly, the model correctly identifies differences in SEV and CL among populations, even with small sample sizes and in cases where the absolute values cannot precisely be recovered. We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling. We demonstrate the utility of our approach with a case study of three bottlenose dolphin populations which appear to possess largely overlapping niches when analyzed with only carbon and nitrogen isotopes. Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

No MeSH data available.


Related in: MedlinePlus

(A) Bottlenose dolphin and approximate ranges for inshore (yellow), coastal (red), and offshore (blue) populations inhabiting the Gulf coast off western Florida. Ranges for offshore and coastal dolphins are illustrative only, as little is known about their exact movements. (B) The estimated isotopic niches for the inshore (yellow), coastal (red), and offshore (blue) populations graphed in three dimensions. (C–E) Three‐dimensional ellipsoids compressed to three‐two‐dimensional plots. (F) Estimated standard ellipsoid volume (SEV) and centroid location (CL) values (median and 95% CI range) for each of the three populations. (G) The SEV column shows the probability that the first listed population has a greater SEV value than the second listed population. The second column shows the estimated differences in CL in pairwise comparisons between populations and the final column lists the probability that the two population have different CL values. (H) The area of overlap between each population divided by the SEV of the population listed in the row to produce the percent of niche overlap (median and 95% CI range).
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ece32013-fig-0002: (A) Bottlenose dolphin and approximate ranges for inshore (yellow), coastal (red), and offshore (blue) populations inhabiting the Gulf coast off western Florida. Ranges for offshore and coastal dolphins are illustrative only, as little is known about their exact movements. (B) The estimated isotopic niches for the inshore (yellow), coastal (red), and offshore (blue) populations graphed in three dimensions. (C–E) Three‐dimensional ellipsoids compressed to three‐two‐dimensional plots. (F) Estimated standard ellipsoid volume (SEV) and centroid location (CL) values (median and 95% CI range) for each of the three populations. (G) The SEV column shows the probability that the first listed population has a greater SEV value than the second listed population. The second column shows the estimated differences in CL in pairwise comparisons between populations and the final column lists the probability that the two population have different CL values. (H) The area of overlap between each population divided by the SEV of the population listed in the row to produce the percent of niche overlap (median and 95% CI range).

Mentions: Common bottlenose dolphins (Tursiops truncatus) possess a nearly pan‐global distribution, with few natural barriers preventing dispersion and gene flow. Yet, populations within close geographic proximity often show considerable genetic distinction (Wells 2014) because differences in habitat use or prey type can facilitate segregation in social interactions (Natoli et al. 2005). Such segregation can be identified via stable isotope analysis. For example, carbon isotope values vary between benthic primary production (i.e., seagrass) and phytoplankton‐dominated, pelagic habitats; nitrogen isotope values are positively correlated with trophic level; and sulfur isotope values increase with salinity (Newsome et al. 2010). Together, these three stable isotopes provide detailed information on both scenopoetic and bionomic niche axes by which we can test for niche segregation among three putative bottlenose dolphin populations inhabiting the Gulf of Mexico (Fig. 2A). The first population (inshore) is comprised of resident dolphins that predominantly utilize shallow waters, often between the mainland and barrier islands. The second group (coastal) contains dolphins that are hypothesized to use shallow waters beyond the barrier islands. The third population (offshore) encompasses dolphins that use waters beyond the continental shelf and have been known to differ morphologically from the inshore and coastal populations.


Beyond carbon and nitrogen: guidelines for estimating three-dimensional isotopic niche space.

Rossman S, Ostrom PH, Gordon F, Zipkin EF - Ecol Evol (2016)

(A) Bottlenose dolphin and approximate ranges for inshore (yellow), coastal (red), and offshore (blue) populations inhabiting the Gulf coast off western Florida. Ranges for offshore and coastal dolphins are illustrative only, as little is known about their exact movements. (B) The estimated isotopic niches for the inshore (yellow), coastal (red), and offshore (blue) populations graphed in three dimensions. (C–E) Three‐dimensional ellipsoids compressed to three‐two‐dimensional plots. (F) Estimated standard ellipsoid volume (SEV) and centroid location (CL) values (median and 95% CI range) for each of the three populations. (G) The SEV column shows the probability that the first listed population has a greater SEV value than the second listed population. The second column shows the estimated differences in CL in pairwise comparisons between populations and the final column lists the probability that the two population have different CL values. (H) The area of overlap between each population divided by the SEV of the population listed in the row to produce the percent of niche overlap (median and 95% CI range).
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4834325&req=5

ece32013-fig-0002: (A) Bottlenose dolphin and approximate ranges for inshore (yellow), coastal (red), and offshore (blue) populations inhabiting the Gulf coast off western Florida. Ranges for offshore and coastal dolphins are illustrative only, as little is known about their exact movements. (B) The estimated isotopic niches for the inshore (yellow), coastal (red), and offshore (blue) populations graphed in three dimensions. (C–E) Three‐dimensional ellipsoids compressed to three‐two‐dimensional plots. (F) Estimated standard ellipsoid volume (SEV) and centroid location (CL) values (median and 95% CI range) for each of the three populations. (G) The SEV column shows the probability that the first listed population has a greater SEV value than the second listed population. The second column shows the estimated differences in CL in pairwise comparisons between populations and the final column lists the probability that the two population have different CL values. (H) The area of overlap between each population divided by the SEV of the population listed in the row to produce the percent of niche overlap (median and 95% CI range).
Mentions: Common bottlenose dolphins (Tursiops truncatus) possess a nearly pan‐global distribution, with few natural barriers preventing dispersion and gene flow. Yet, populations within close geographic proximity often show considerable genetic distinction (Wells 2014) because differences in habitat use or prey type can facilitate segregation in social interactions (Natoli et al. 2005). Such segregation can be identified via stable isotope analysis. For example, carbon isotope values vary between benthic primary production (i.e., seagrass) and phytoplankton‐dominated, pelagic habitats; nitrogen isotope values are positively correlated with trophic level; and sulfur isotope values increase with salinity (Newsome et al. 2010). Together, these three stable isotopes provide detailed information on both scenopoetic and bionomic niche axes by which we can test for niche segregation among three putative bottlenose dolphin populations inhabiting the Gulf of Mexico (Fig. 2A). The first population (inshore) is comprised of resident dolphins that predominantly utilize shallow waters, often between the mainland and barrier islands. The second group (coastal) contains dolphins that are hypothesized to use shallow waters beyond the barrier islands. The third population (offshore) encompasses dolphins that use waters beyond the continental shelf and have been known to differ morphologically from the inshore and coastal populations.

Bottom Line: Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use.We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling.Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative BiologyMichigan State UniversityEast LansingMichigan48824; Ecology Evolutionary Biology and Behavior ProgramMichigan State UniversityEast LansingMichigan48824; Hubbs-Sea World Research Institute3830 S. Highway A1A #4-181Melbourne BeachFlorida32951.

ABSTRACT
Isotopic niche has typically been characterized through carbon and nitrogen ratios and most modeling approaches are limited to two dimensions. Yet, other stable isotopes can provide additional power to resolve questions associated with foraging, migration, dispersal and variations in resource use. The ellipse niche model was recently generalized to n-dimensions. We present an analogous methodology which incorporates variation across three stable dimensions to estimate the significant features of a population's isotopic niche space including: 1) niche volume (referred to as standard ellipsoid volume, SEV), 2) relative centroid location (CL), 3) shape and 4) area of overlap between multiple ellipsoids and 5) distance between two CLs. We conducted a simulation study showing the accuracy and precision of three dimensional niche models across a range of values. Importantly, the model correctly identifies differences in SEV and CL among populations, even with small sample sizes and in cases where the absolute values cannot precisely be recovered. We use these results to provide guidelines for sample size in conducting multivariate isotopic niche modeling. We demonstrate the utility of our approach with a case study of three bottlenose dolphin populations which appear to possess largely overlapping niches when analyzed with only carbon and nitrogen isotopes. Upon inclusion of sulfur, we see that the three dolphin ecotypes are in fact segregated on the basis of salinity and find the stable isotope niche of inshore bottlenose dolphins significantly larger than coastal and offshore populations.

No MeSH data available.


Related in: MedlinePlus