Body size dependent dispersal influences stability in heterogeneous metacommunities

Kurt E Anderson,Ashkaan K Fahimipour

doi:10.1038/s41598-021-96629-5

Abstract

Body size affects key biological processes across the tree of life, with particular importance for food web dynamics and stability. Traits influencing movement capabilities depend strongly on body size, yet the effects of allometrically-structured dispersal on food web stability are less well understood than other demographic processes. Here we study the stability properties of spatially-arranged model food webs in which larger bodied species occupy higher trophic positions, while species’ body sizes also determine the rates at which they traverse spatial networks of heterogeneous habitat patches. Our analysis shows an apparent stabilizing effect of positive dispersal rate scaling with body size compared to negative scaling relationships or uniform dispersal. However, as the global coupling strength among patches increases, the benefits of positive body size-dispersal scaling disappear. A permutational analysis shows that breaking allometric dispersal hierarchies while preserving dispersal rate distributions rarely alters qualitative aspects of metacommunity stability. Taken together, these results suggest that the oft-predicted stabilizing effects of large mobile predators may, for some dimensions of ecological stability, be attributed to increased patch coupling per se, and not necessarily coupling by top trophic levels in particular.

Highlights

Food web diversity than can be supported in isolated well-mixed systems[18]
We assume that body size structures the underlying food web and that dispersal rates follow simple allometric scaling rules, similar to locomotive capabilities and space use patterns
We found that increased connectivity, manifested either through larger values of global patch coupling d or stronger positive body size-dispersal scaling z, generates conditions in which fewer stable patches are required for the metacommunity they comprise to be stable (Fig. 2)

Summary

Introduction

Food web diversity than can be supported in isolated well-mixed systems[18]. Dispersal can stabilize species interactions locally by mimicking density-dependence in per capita growth r ates[40,41,42,43]. While locomotion and space use do not necessarily equate to dispersal, these patterns do in turn create the potential for body size to influence spatial coupling of habitat patches[55] and local food webs[19,56,57]. We examine how body size scaling of species’ dispersal rates influences stability in model trophic metacommunities (Fig. 1). We ask whether body size-dependent variation in dispersal rates influences trophic metacommunity stability relative to rates that are either uniform or randomly varying among species. We assume that body size structures the underlying food web and that dispersal rates follow simple allometric scaling rules, similar to locomotive capabilities and space use patterns. Our results show strong effects of dispersal-body size scaling on metacommunity stability, largely due to increased connectivity among local webs with different stability properties

Methods

Results

Conclusion