DESIGN AND ANALYSIS OF MULTISPECIES TOXICITY TESTS FOR PESTICIDE REGISTRATION

The community conditioning hypothesis describes ecological structures as historical, nonequilibrial, and by definition complex. Indeed, the historical nature of ecological structures is seen as the primary diff erence between single-species toxicity tests and multispecies test sys tems. Given the complex properties of ecological structures, multispec ies toxicity tests need to be designed accordingly with appropriate da ta analysis tools. Care must be taken to ensure that each replicate sh ares an identical history, or divergence will rapidly occur. Attemptin g to realize homogeneity by linear cross inoculation or waiting for an equilibrium state to occur assumes properties that ecological structu res do not have. Data analysis must also incorporate the dynamic and h yperdimensional nature of ecological structures. Univariate analysis o f individual variables denies the fundamental character of ecological structures as complex systems. A variety of methods, such as correspon dence analysis, nonmetric multidimensional scaling, and nonmetric clus tering and association analysis, are available to search for patterns and to test their relationships to experimental treatments. Visualizat ion techniques including Space-Time Worms and redundancy analysis are also critical in attempting to understand the dynamic nature of these structures. Reliance upon the traditional analysis methods, such as AN OVA and the estimation of LOECs (lowest observable effects concentrati ons) or NOECs (no observable effects concentrations), comparable to th ose of single-species toxicity tests, is to be blind to the unique and complex nature of multispecies toxicity tests. Fundamental design cri teria for multispecies toxicity tests, data analysis, and interpretati on are presented.