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.

Chemical Ecology is a component of Encyclopedia of Chemical Sciences, Engineering and Technology Resources in the global Encyclopedia of Life Support Systems (EOLSS), which is an integrated compendium of twenty one Encyclopedias. The Theme on Chemical Ecology provides the essential aspects of the chemicals involved in the interactions of living organisms. It deals with studies involving defensive chemicals which are utilized to deter potential predators, which may attack a wide variety of species, animal interaction, aquatic ecosystems, chemical ecology and pest management, relation to medicine and pharmaceuticals. This volume is aimed at the following five major target audiences: University and College students Educators, Professional practitioners, Research personnel and Policy analysts, managers, and decision makers.

Chemical signals mediate all aspects of insects' lives and their ecological interactions. The discipline of chemical ecology seeks to unravel these interactions by identifying and defining the chemicals involved, and documenting how perception of these chemical mediators modifies behaviour and ultimately reproductive success. Chapters in this 2004 volume consider how plants use chemicals to defend themselves from insect herbivores; the complexity of floral odors that mediate insect pollination; tritrophic interactions of plants, herbivores, and parasitoids and the chemical cues that parasitoids use to find their herbivore hosts; the semiochemically mediated behaviours of mites; pheromone communication in spiders and cockroaches; the ecological dependency of tiger moths on the chemistry of their host-plants; and the selective forces that shape the pheromone communication channel of moths. The volume presents descriptions of the chemicals involved, the effects of semiochemically mediated interactions on reproductive success, and the evolutionary pathways that have shaped the chemical ecology of arthropods.

The 11th International Symposium on Insect-Plant Relationships (SIP11), held on August 4-10, 2001, in Helsingør, Denmark, followed the tradition of previous SIP meetings and covered topics of different levels from chemistry, physiology, and ethology to ecology, genetics, and evolution of insect-plant relationships. The present volume includes a representative selection of fully refereed papers as well as a complete list of all the contributions which were presented at the meeting. Reviews of selected topics as well as original experimental data are included. The book provides valuable information for students and research workers interested in chemical and biological aspects of interactions between individuals and populations of different organisms.

Plant secondary metabolites (PSMs) such as terpenes and phenolic compounds are known to have numerous ecological roles, notably in defence against herbivores, pathogens and abiotic stresses and in interactions with competitors and mutualists. This book reviews recent developments in the field to provide a synthesis of the function, ecology and evolution of PSMs, revealing our increased awareness of their integrative role in connecting natural systems. It emphasises the multiple roles of secondary metabolites in mediating the interactions between organisms and their environment at a range of scales of ecological organisation, demonstrating how genes encoding for PSM biosynthetic enzymes can have effects from the cellular scale within individual plants all the way to global environmental processes. A range of recent methodological advances, including molecular, transgenic and metabolomic techniques, are illustrated and promising directions for future studies are identified, making this a valuable reference for researchers and graduate students in the field.

Identification of chemicals that affect the naturally occurring interactions be tween organisms requires sophisticated chemical techniques, such as those docu mented in volume 1, in combination with effective bioassays. Without an effective bioassay, the identification becomes akin to looking for a needle in a haystack, but without any idea of what a needle looks like. To a large extent serniochemical identifications must be driven by bioassays. The design of bioassays for use in chemical ecology is governed by the sometimes conflicting objectives of ecological relevance and the need for simplic ity. Bioassay design should be based on observations of the interactions between organisms in their natural context, a theme that appears throughout this volume. As a result, this volume is as much about ecology and behavior as it is about specific methods. It is impossible to design a relevant bioassay, whether it is simple or complex, without understanding at least the fundamentals of how chemical cues or signals mediate the interaction in nature. Thus, the development of bioassay methods must be driven by an understanding of ecology and a knowledge of the natural history of the organisms under study. Given such an understanding, it is often possible to design assays that are both ecologically relevant and easy to perform.

Microbiologists and soil scientists will find this study compelling reading. It focuses on the role of bacterial, fungal and plant secondary metabolites in soil ecosystems. Our understanding of the biological function of secondary metabolites is surprisingly limited, considering our knowledge of their structural diversity and pharmaceutical activity. This book reviews functional aspects of secondary metabolite production, with a focus on interactions among soil organisms.