What determines trophic niche breadth? A global analysis of freshwater fishes using isospaces
Document Type
Article
Publication Date
12-1-2026
Abstract
Understanding the factors shaping trophic niche breadth is crucial for predicting species interactions, community assembly, and ecological responses to environmental change. Several hypotheses have been proposed to explain global variation in species' trophic niches, but empirical tests are limited. Here, we used stable isotope analysis (δ13C and δ15N) to quantify trophic niche breadth of 541 fish populations (358 species, 82 families) from freshwater ecosystems encompassing diverse environmental conditions and six biogeographic regions. Fourteen hypotheses relating niche breadth to environmental factors, traits, and sampling scale were tested. Fish isospaces were broader in regions with warmer temperatures, higher humidity, and precipitation variability, suggesting that more productive, diverse, and seasonal ecosystems are associated with broader trophic niches. Conversely, isospace size declined with increasing basin fish richness, which may reflect the role of competitive interactions. Within-population variation in body size was strongly and positively associated with isospace size, indicating ontogenetic dietary shifts. Fish with truncate-rounded fins had broader isospaces than those with forked-lunate fins, likely reflecting differences in foraging behavior and movement. Primary consumers had larger isospaces than intermediate and top consumers. Predators showed patterns similar to those across all trophic guilds, but non-predators differed in relation to solar radiation, richness, body size, and fin shape. Isospace size increased with the number of sampled individuals, habitats and years surveyed. Although isospace patterns have well-documented limitations as trophic ecology metrics, our findings nonetheless conform with several longstanding hypotheses for trophic niche variation and stimulate new ideas about environmental and biological drivers of niche breadth.
Publication Title
Reviews in Fish Biology and Fisheries
Recommended Citation
Keppeler, F.,
Giarrizzo, T.,
Montaña, C.,
Adite, A.,
Akın, Ş.,
Angelini, R.,
Arantes, C.,
Benedito, E.,
Bokhutlo, T.,
El-Sabaawi, R.,
Garcia, A.,
Gonzalez-Bergonzoni, I.,
Hoeinghaus, D.,
Hoffman, J.,
Jensen, O.,
Jeppesen, E.,
Kopf, R.,
Layman, C.,
Lopez, E.,
Maitland, B.,
Matsuzaki, S.,
Olin, J.,
Paterson, G.,
Quintana, Y.,
de Rezende, C.,
Trudeau, A.,
Trindade, P.,
Turner, T.,
Zandona, E.,
&
Winemiller, K.
(2026).
What determines trophic niche breadth? A global analysis of freshwater fishes using isospaces.
Reviews in Fish Biology and Fisheries,
36(1).
http://doi.org/10.1007/s11160-025-10023-2
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p2/2290