Abstract
Ontogenetic niche shifts occur across diverse taxonomic groups, and can have critical implications for population dynamics, community structure, and ecosystem function. In this study, we provide a hypothesis-testing framework combining univariate and multivariate analyses to examine ontogenetic niche shifts using stable isotope ratios. This framework is based on three distinct ontogenetic niche shift scenarios, i.e., (1) no niche shift, (2) niche expansion/reduction, and (3) discrete niche shift between size classes. We developed criteria for identifying each scenario, as based on three important resource use characteristics, i.e., niche width, niche position, and niche overlap. We provide an empirical example for each ontogenetic niche shift scenario, illustrating differences in resource use characteristics among different organisms. The present framework provides a foundation for future studies on ontogenetic niche shifts, and also can be applied to examine resource variability among other population sub-groupings (e.g., by sex or phenotype).
Highlights
Changes in resource use with body size or age, i.e., ontogenetic niche shifts, may occur in 80% of animal taxa [1], and have been shown to affect the structure and dynamics of populations, communities and ecosystems [1,2,3]
Juvenile (n = 31, size range: 40–96mm Standard Length (SL)) and sub-adult (n = 89, size range: 101–204mm SL) L. griseus differed significantly in their (1) niche width, which was driven by a difference in variance of d13C values (Bartlett: K2 = 10.37, df = 1, P = 0.001), not d15N (Bartlett: K2 = 1.07, df = 1, P = 0.3)
There was no shift in (2) isotopic niche position (Euclidean distance = 0.94, P = 0.13; Fig. 3B) and (3) most juvenile L. griseus overlapped with the niche width of sub-adults (97% of individuals), whereas only 35% of sub-adults were encompassed by the convex hull of the juveniles (Fig. 3B)
Summary
Changes in resource use with body size or age, i.e., ontogenetic niche shifts, may occur in 80% of animal taxa [1], and have been shown to affect the structure and dynamics of populations, communities and ecosystems [1,2,3]. Species often feed at higher trophic levels as they mature [4,5] and interactions with other species may shift from competition to predation through ontogeny [6,7] Many organisms increase their foraging range with ontogeny [8], thereby changing the nature of nutrient and energy flow through different habitats or ecosystems [9]. Consumers may switch to a different resource pool during ontogenetic development (Fig. 1C, 1F), e.g., those organisms that have different diets following metamorphosis [14] or following shifts across habitat boundaries [15,16,17] These different ontogenetic niche shift scenarios will translate into changes in niche width, niche position and/or niche overlap between size classes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
