Assessing body-size dependence in dispersal influences stability in heterogeneous metacommunities
Body size affects key biological processes across the tree of life, with particular importance for food web dynamics and stability. Traits influencing dispersal capabilities depend strongly on body size, yet the effects of allometric dispersal on food web stability are less well understood than other demographic processes. Food webs were assembled such that larger bodied species occupy higher trophic positions while species' body sizes also determine the rates at which they traverse a spatial network of heterogeneous habitat patches. Strong positive scaling of dispersal rate with body-size appears to stabilize metacommunities compared to negative scaling relationships or completely uniform dispersal. However, when global coupling among patches is strong enough, the benefits of a positive body-size scaling of dispersal rate disappear. A permutational analysis shows that breaking the body-size dispersal hierarchy 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-bodied mobile predators may, for some dimensions of ecological stability, be attributed to increased patch coupling per se, and not necessarily by top trophic levels in particular.
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