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

Area of Science:

• Ecology
• Stable Isotope Ecology
• Population Ecology

Background:

• Traditional isotopic niche characterization relies on carbon and nitrogen, limiting ecological insights.
• Existing models often restrict analysis to two dimensions, potentially obscuring population-level variations.
• Stable isotopes offer powerful, multi-dimensional data for understanding foraging, migration, and resource use.

Purpose of the Study:

• To develop and validate a multivariate methodology for estimating isotopic niche space in three dimensions.
• To quantify key niche features: niche volume (standard ellipsoid volume, SEV), centroid location (CL), shape, overlap, and distance between CLs.
• To provide guidelines for sample size in multivariate isotopic niche modeling.

Main Methods:

• Generalization of the n-dimensional ellipse niche model to three stable isotope dimensions.
• Conducting simulation studies to assess the accuracy and precision of the 3D niche models.
• Application of the 3D niche modeling approach to analyze three bottlenose dolphin populations using carbon, nitrogen, and sulfur isotopes.

Main Results:

• The 3D niche model accurately identifies differences in SEV and CL among populations, even with small sample sizes.
• The model demonstrates precision in recovering niche parameters, though absolute values may require larger sample sizes.
• In bottlenose dolphins, incorporating sulfur isotopes revealed significant segregation based on salinity, unlike 2D models.

Conclusions:

• Three-dimensional stable isotope niche modeling provides a more robust framework for ecological studies.
• The inclusion of additional isotopes like sulfur can resolve population structure previously obscured by 2D analyses.
• This approach enhances our understanding of ecological niche differentiation and informs sample size requirements for future studies.