Food-web coupling by mobile consumers has individual to ecosystem level effects

Abstract

Mobile consumers serve as a ubiquitous link, coupling the dynamics and functions of different ecosystems, ranging from diel-vertical migration of zooplankton to seasonal movements of large ungulates. Despite mounting theoretical interest, experimental tests of the effects of consumer mobility in meta-ecosystems are virtually non-existent. Here, we used an experimental microcosm system to investigate how mobile consumers (Daphnia magna) mediate ecosystem biomass, community structure, and their own fitness by coupling spatially distinct aquatic ecosystems composed of two different protist communities. We found that consumer mobility significantly influenced the effect of consumption on ecosystem biomass and the growth and reproduction of the consumers, themselves. However, the direction and magnitude of these effects depended on community composition in the connected ecosystem. Further, we found consumer mobility consistently promoted the coexistence of a competing local species, regardless of community composition in the connected ecosystem. Our findings underscore the profound role of consumer mobility in shaping individual to ecosystem-level dynamics while emphasizing a strong mediating effect of community composition across the landscape.