PARENT SESSION
Oral Session #46: Animal Community Ecology: Pools, Foodwebs, Structure. Presiding: D. Post.
Wednesday, August 8, 2001. 8:00 AM to 12:00 PM. Hall of Ideas I.
Stability and complexity in microcosm ecosystems.
Fox, Jeremy1, Barreto, Cristine2, 1 2
ABSTRACT- Consumers often feed in a patchy landscape, where patches offer variable risks and rewards. Most experimental work has examined the optimality of patch choice by individual consumers, with the community-level consequences of patchiness receiving less attention. We conducted protist microcosm experiments testing the effect of patchiness on coexistence of ciliates competing for bacteria. Bacteria tended to grow in dense patches on the bottom of the microcosms. Eliminating bacterial patches by continuously shaking the microcosms reduced coexistence between competing ciliates. In unshaken microcosms, some ciliates aggregate in dense patches of bacteria, apparently increasing the intensity of intraspecific competition and promoting coexistence. We also tested the effects of prey refuges on predator-prey interactions. Adding glass beads to the microcosms created crevices which sheltered small ciliate prey from large protist predators. Refuges prolonged the persistence of unstable predator-prey interactions, altered the persistence of prey too large to use the refuges, and changed the response of the food web to increased productivity. More research is needed to assess the circumstances under which patchiness can be ignored, and when it must be included in community models.
KEY WORDS: protists, microcosms, spatial structure, consumer-resource interactions