Community structure and collapses in multichannel food webs: Role of consumer body sizes and mesohabitat productivities

Abstract

Multichannel food webs are shaped by the ability of apex predators to link asymmetric energy flows in mesohabitats differing in productivity and community traits. While body size is a fundamental trait underlying life histories and demography, its implications for structuring multichannel food webs are unexplored. To fill this gap, we develop a model that links population responses to predation, and resource availability to community‐level patterns, using a tri‐trophic food web model with two populations of intermediate consumers and a size‐selective top predator. We show that asymmetries in mesohabitat productivities and consumer body sizes drive food web structure, merging previously separate theory on apparent competition and emergent Allee effects (i.e. abrupt population collapses) of top predators. Our results yield theoretical support for empirically observed stability of asymmetric multichannel food webs and discover three novel types of emergent Allee effects involving intermediate consumers, multiple populations or multiple alternative stable states.

The effect of environmental stressors on growth in fish and its endocrine control

“…Fish growth rate is an important trait with ecological, evolutionary, and conservation implications ( 1 , 2 ). Anthropogenic stressors such as global climate change, which imply temperature rise, salinity change, and ocean acidification; ecosystem disturbance; and selective pressure from capture have shown a rapid effect on the growth rate of several fish species ( 2 – 10 ). During the last century, the mean global temperatures have risen approximately 1.1°C concurrently with increasing anthropogenic greenhouse gas emissions ( 11 ).…”

Trophic ontogeny of a generalist predator is conserved across space

“…The diet of most animals can vary tremendously with their age and body size (Wilbur 1980; Werner and Gilliam 1984; Krenek and Rudolf 2014). Understanding how diet changes with ontogeny can allow us to link the size structure of consumers with their trophic roles and contributions to the ow of energy through ecosystems (Layman et al 2015), and may further help us to characterize the architecture of food webs (Brose et al 2006;Dijoux & Boukal 2021). Historically, ecologists have used a number of methods (e.g., gut contents, observations of animals eating, fecal analysis) to build models to describe how species change their diets through ontogeny.…”

Body size and trophic position determine the outcomes of species invasions along temperature and productivity gradients

“…Among species traits, individual body mass can be used to predict invasibility because it affects individual fitness, species interactions and energy flows (McCann & Rooney 2009;Brose et al 2017;Dijoux & Boukal 2021). For example, larger species tend to prey on smaller species, especially in aquatic habitats (Ou et al 2017) and warming-induced metabolic meltdown is more likely for larger consumers than smaller ones (Rall et al 2010.…”