PARENT SESSION
Symposium 21: Miniature Worlds? Natural Microcosms as Model Ecological Systems
Organized by: D Srivastava and J Kolasa
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Chatham Ballroom C.

Should ecologists throw away their petri dishes and aquaria?

Lawler, Sharon^*,1, ¹ University of California, Davis, CA, USA

ABSTRACT- Understanding of the limitations and benefits of microcosm studies is essential to their use in ecology. Microcosms are sometimes too small to allow full expression of processes that may be important at larger scales (e.g., migration). Scale transitions usually prevent quantitative extrapolation of microcosm results. They are prone to artifacts including wall effects, build-up of toxins, chemical imbalances, sampling depletion, and isolation from environmental and biotic conditions that were of unforeseen importance. Note that careful examination of isolation effects and other artifacts may advance theory by revealing overlooked factors. On the positive side, creative microcosm experiments can provide powerful evaluation of theory and mechanisms, yielding testable, if qualitative, predictions for large systems. Well-known advantages of microcosm research include replicability, control, ease of manipulation and sampling, and the opportunity to observe population dynamics. Like any experimental system, microcosms vary in levels of realism. 'Minature worlds' (e.g., phytotelmata, rock pools) provide elements of realism missing from laboratory microcosms, such as realistic levels of environmental heterogeneity, disturbance, dispersal, and variation in community structure. Given these advantages, natural microcosms are a better choice for testing some aspects of ecological theory, especially if the robustness of theory to a variable world is a concern. However, it is more difficult to prove mechanisms or to dissect signal from noise when environmental and biotic conditions are less controlled. Some kinds of theory are more easily tested in laboratory microcosms than natural microcosms. Examples include theories about environmental noise and resonance, and theory pertaining to evolutionary ecology. In general, fears that microcosm results will mislead science have not been borne out. Instead, microcosms have served as an essential link in the scientific cycle of observation, development of theory, and experimental tests that lead to new observations and refinement of theory.

Key words: scale effects, microcosms, experimental artifacts