Critical patch sizes for food‐web modules

Because patch size and connectivity may strongly impact the assemblage of species that occur on a patch, the types of food-web interactions that occur among those species may also depend on spatial structure. Here, we identify whether food-web interactions among salt-marsh-inhabiting arthropods vary with patch size and connectivity, and how such changes in trophic structure might feed back to influence the spatial distribution of prey. In a multiyear survey, patch-restricted predators exhibited steeper occupancy–patch-size relationships than herbivores, and species' critical patch sizes were correlated with overall rarity. As a result, the presence of food-web modules depended strongly on patch size: large and well-connected patches supported complex food-web modules, but only the simplest modules involving the most abundant species were found on small patches. Habitat-generalist spiders dominated on small patches, and predation pressure from such species may contribute to the observed lower densities of ...