Does the strength of cross‐ecosystem trophic cascades vary with ecosystem size? A test using a natural microcosm

摘要: Summary The cascading effect of predators on the functioning adjacent ecosystems can occur when life cycles their prey include two ecosystems. However, there has been little consideration which habitat attributes modify strength these cross-ecosystem trophic cascades. Habitat size mediate predator–prey interactions, and thus affect within-ecosystem We hypothesise that similar effects might cascades. It shown terrestrial (e.g. spiders) capture adult insects as they attempt to oviposit in waters bromeliads. Such could therefore alter structure aquatic food web. If spiders an level is influenced by bromeliad size, then cascade will also depend size. To test this general hypothesis, we manipulated presence a funnel-web spider (Aglaoctenus castaneus, Lycosidae), builds single web over water-filled bromeliads, bromeliads differing examined invertebrate community ecosystem functions (decomposition, detrital nitrogen flux). The were largely independent size. Spiders did initiate changes webs, reducing biomass predators, especially damselflies dytiscid beetles. increased decomposition despite having no detritivore or composition. These results are most parsimoniously explained (i) behaviourally mediated cascade, whereby damselfly adults avoid with spiders, detritivores increase rates processing absence larvae, (ii) stimulation through nutrients added from faeces carcasses. believe first study show flux keystone complex cycles.