Allometry in an eco-evolutionary network model

Abstract

An eco-evolutionary food web model is modified to incorporate a body-size trait, enabling a framework for nonuniform mortality and ecological efficiency between species. Evolved communities feature increased connectance, with according benefits to community robustness, and persistent top predators but reduced omnivory and food chain lengths. Body-size maintains a strong positive correlation to trophic level, but does not correlate to an individual species' contribution to network stability. A spatially-explicit extension of the model assembles large metacommunities with distinct distributions of body-size amongst local food webs.

Sequences of patch disturbance in a spatial eco-evolutionary model

“…Different rules can be utilised to govern the movement of populations between adjacent patches on the spatial network. Recently, we implemented allometric scaling [46], inspired by Brännström et al's version [47] of the alternative Loeuille-Loreau eco-evolutionary model [48]. This modification assigns an additional continuous bodysize trait to each species, so that they loosely prefer to feed on other species within a suitable window of smaller bodysizes.…”

“…Next, the ecological efficiency 0 < λ < 1 controls the efficiency of energy transfer between the trophic levels. It is set at 0.3 as in previous investigations with this model variant [46], but a higher or lower value would result in longer or shorter food chains and thus higher or lower maximum trophic levels, respectively. Finally, the available new biomass is divided by body-size s i to yield the number of new members of the population of species i that result.…”

“…This allows local populations to update their feeding efforts in response to the current conditions and the success of their previous strategy, and in turn their ratiodependent functional responses g i,j for each prey species j are updated based on the division of their feeding efforts and the traits possessed by each species. A full description of this mechanism is provided in [46].…”

“…The amount of the remaining population that emigrates is proportional to the severity of the decrease since the previous ecological timestep. This scheme is an allometrically-scaled version of the adaptive migration used in our previous spatial extension of Webworld [45,46] where it was demonstrated to construct meta-communities of highly-diverse and distinct food webs. More generally, adaptive migration has been shown to improve species persistence in other work, including recent nonevolutionary models [51].…”

Perturbation responses in co‐evolved model meta‐communities

“…This study uses a previously described spatial eco‐evolutionary model (Abernethy, 2020 ) to generate a set of abstract trait‐based meta‐communities which are subjected to perturbations at both the species and patch level and tested for optimal placement of reserves in the spatial network. This has been developed from an extension of the Webworld eco‐evolutionary model (Drossel et al, 2001 ).…”