A hypothesis-testing framework for studies investigating ontogenetic niche shifts using stable isotope ratios

Area of Science:

• Ecology
• Evolutionary Biology
• Stable Isotope Ecology

Background:

• Ontogenetic niche shifts are crucial for understanding population dynamics, community structure, and ecosystem function.
• These shifts, where an organism's ecological niche changes with age or size, are observed across many taxa.
• Stable isotope analysis offers a powerful tool to investigate these dietary and habitat changes.

Purpose of the Study:

• To develop and present a hypothesis-testing framework for examining ontogenetic niche shifts.
• To integrate univariate and multivariate analyses using stable isotope data.
• To define and differentiate three key scenarios of ontogenetic niche shifts.

Main Methods:

• Utilized stable isotope ratios (e.g., d13C, d15N) to assess resource use.
• Developed criteria based on niche width, niche position, and niche overlap to identify shift scenarios.
• Applied a combination of univariate and multivariate statistical analyses.

Main Results:

• The framework successfully categorizes ontogenetic niche shifts into three distinct scenarios: no shift, niche expansion/reduction, and discrete niche shift.
• Empirical examples demonstrated differences in resource use characteristics among various organisms across these scenarios.
• Provided clear criteria for identifying each niche shift type.

Conclusions:

• The proposed framework offers a robust foundation for future research on ontogenetic niche shifts.
• This approach can be extended to analyze resource variability in other population sub-groupings, such as by sex or phenotype.
• Understanding ontogenetic niche shifts is vital for predicting ecological responses to environmental change.