On the evolution of trophic position

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.