Diversity within and among living organisms is both a biological impera-
tive and a biological conundrum. Phenotypic and genotypic diversity is
the critical currency ofecological interactions and the evolution of
life. Thus, it is not unexpected to find vast phytochemical diversity
among plants. However, among the most compelling questions which arise
among those interested in ecological phytochemistry is the extent,
nature, and reasons for the diversity of chemieals in plants. The idea
that natural products (secondary metabolites) are accidents of
metabolism and have no biological function is an old one which has
resurfaced recently under a new term "redundancy. " Redundancy in the
broader sense can be viewed as duplication of effort. The co-occurrence
of several classes of phytochemieals in a given plant may be redundancy.
Is there unnecessary duplication of chemical defense systems and ifso,
why? What selective forces have produced this result? On the other hand,
why does the same compound often have multiple functions? At a symposium
of the Phytochemical Society of North America held in August 1995, in
Sault Ste. Marie, Ontario, Canada, the topic "Phytochernical Redundancy
in Ecological Interactions" was discussed. The chapters in this volume
are based on that symposium. They both stimulate thought and provide
some working hypotheses for future research. It is being increasingly
recognized that functional diversity and multiplicity of function of
natural products is the norm rather than the exception.