On the evolution of trophic position

Abstract

The trophic structure of food webs is primarily determined by the variation in trophic position among species and individuals. Temporal dynamics of food web structure are central to our understanding of energy and nutrient fluxes in changing environments, but little is known about how evolutionary processes shape trophic position variation in natural populations. We propose that trophic position, whose expression depends on both environmental and genetic determinants of the diet variation in individual consumers, is a quantitative trait that can evolve via natural selection. Such evolution can occur either when trophic position is correlated with other heritable morphological and behavioural traits under selection, or when trophic position is a target of selection, which is possible if the fitness effects of prey items are heterogeneously distributed along food chains. Recognising trophic position as an evolving trait, whose expression depends on the food web context, provides an important conceptual link between behavioural foraging theory and food web dynamics, and a useful starting point for the integration of ecological and evolutionary studies of trophic position.

Isotopic niche alteration of a predator fish in a dammed Amazonian black water river

“…The trophic position of the predator indicates the number of trophic levels above the plants at the base of the food chain (Vander‐Zanden et al ., 1997). The variability in the trophic position among populations can be due to changes in the diet of the individual or due to changes in the trophic position of prey organisms (Moosmann et al ., 2021). Therefore, if individuals in the undammed river specialize in predatory prey those individuals may have a higher trophic position than is possible for conspecifics in the dammed system (Layman et al ., 2007b).…”

Artificial selection for predatory behaviour results in dietary niche differentiation in an omnivorous mammal

“…Dietary niche variation can have fitness effects (e.g. in pigeon guillemots [62], isopods [63], toads [60] and insect herbivores [68], see also [7]), thus the observed niche variation could result from the selective survival of those individuals that were able to best adapt their diet to the environment and intraspecific competition.…”

Artificial selection for predatory behavior results in dietary niche differentiation in an omnivorous mammal

“…Dietary niche variation can have fitness effects (e.g. in pigeon guillemots [61], isopods [62], toads [59], and insect herbivores [66], see also [5]), thus the observed niche variation could result from the selective survival of those individuals that were able to best adapt their diet to the environment and intraspecific competition. We observed overall seasonal differences in the isotope ratios in the hair of voles, likely due to the phenology of plants, animals and fungi altering the availability of specific dietary items over the summer.…”

“…Yet, the role of evolved behavioral traits in shaping diet choice remains poorly understood [3] and research has focused primarily on predatory behavior of carnivores, which tend to show more specialization than other trophic groups [2]. Deciphering the relative effects of genetic and environmental influences on realized diets of individuals is challenging but essential for understanding the evolvability and plasticity of the dietary niche [5]. In this study, we address this problem by combining artificial selection for a predatory behavior in an omnivorous mammal with a field experiment.…”

“…The diet an individual consumes is a result of the availability of different food items, the species-specific dietary range, and individual specialization [1,2]. The resulting differences among individuals in dietary niche are generated by environmental and genetic variation as well as phenotypic plasticity [1,2], but the relative effects of these factors have rarely been tested [2][3][4][5]. Inherited effects might manifest through various morphological, physiological, or behavioral traits that shape preferences for certain foods and specialized behaviors connected to seeking or processing food items [3].…”