Plant-Provided Food
for Carnivorous Insects: a Protective Mutualism and Its Applications
F. L. Wäckers, P.C.J. van Rijn and J. Bruin, eds.
Cambridge University Press
Cambridge, 2005, 356 pp., $130.00
ISBN: 0-21-81941-5
Plant-herbivore interactions, trophic cascades, and tritrophic
relationships are nonrandom associations that have been the subject
of much interest among evolutionary and ecological entomologists.
Issues such as evolutionary pathways of plant-insect relationships,
chemical mechanisms responsible for these relationships, and their
population-, community-, and ecosystem-level consequences have
captivated researchers' interest not only for their basic ecological
implications, but also for their importance in applied areas such as
biological control. In this context, Plant-Provided Food for
Carnivorous Insects: A Protective Mutualism and Its Applications
provides a novel perspective on plant-herbivore-carnivore
relationships. Instead of emphasizing the influence that plants and
herbivores have on carnivores, this book focuses on the
environmental requirements, evolutionary pathways, and ecological
functions of the natural enemies themselves.
This book is organized in an introductory chapter and three
sections. The first section is comprised of three chapters that
emphasize the resources provided by plants, as well as the
evolutionary ecology of plant-insect interactions. The first chapter
of this section provides a comprehensive review of the physical and
chemical characteristics of different types of plant-provided food
as well as the factors that can affect their suitability for
omnivores. This chapter provides much of the information needed to
critically evaluate the potential use of food supplements to
increase the effectiveness of predators and parasitoids in
suppressing prey populations. The last two chapters of this section
examine hypotheses and associated evidences that food-for-protection
mutualisms are widespread patterns and that they provide important
fitness consequences to plants. However, some of the evidence cited,
as well as the lack of information regarding other aspects of the
evolution of these mutualisms (such as their persistence in the face
of potential exploitation), suggest that that there is still much
room for additional theoretical and empirical studies.
The second section of the book focuses on arthropods' feeding
habits. Overall, these chapters highlight that high-nitrogen food
resources such as pollen, seeds, and pods can have a large impact on
omnivore arthropod populations. With much detail, these chapters
describe how the quantity, quality, and accessibility of food
resources interact with natural enemies behavioral patterns and
morphological structures. They further explore how these resources
impact plant-omnivore-prey dynamics. As the authors point out,
little is known about the mechanisms by which these interactions
occur. Unfortunately, for the most part, this section fails to
provide a comprehensive list of research questions demanding
additional studies. However, the authors do recommend a few areas
ripe for further research, including quantifying the effect of plant
feeding on omnivore-prey interactions, understanding the functional
and numerical response of omnivorous predators, and comparing the
relative impact of strict predators versus omnivores in suppressing
prey populations. Ultimately, answering these questions will provide
the necessary knowledge to design applied biological control
programs based on the functional importance of biodiversity.
The third section of the book is comprised of four papers on the
importance of plant-provided food for biological control with
examples of how habitat diversification could enhance the
survivorship of beneficial insects in highly simplified and
disturbed settings such as modern agroecosystems. Although
appealing, the concept that habitat management can be used to
promote natural enemies of agricultural pests is not a new one and
has been previously discussed in other books (Barbosa
1998, Pickett and Bugg 1998,
Hawkins and Cornell 1999).
Consequently, little in this section could be considered new
information. The most novel contribution in this section is the
chapter by Gurr and collaborators that critically review ecological
theory to improve conservation biological control, pointing out that
a "shotgun approach" to enhance habitat diversity could result in
unintended negative consequences. They further suggest that in
agricultural systems, the use of mathematical modeling, and risk
analysis are valid means to increase the success rate of
conservation biological control programs.
This book is a timely review for entomologists and biological
control specialists interested in the evolutionary and ecological
importance of omnivorous multitrophic interactions. Its exhaustive
literature review could be helpful to graduate students and
researchers interested in food-web ecology in both natural and
managed systems. Unfortunately, it is often left up to the reader to
figure out where the most productive future research questions are.
References
Conservation biological control. P Barbosa, ed. New York, Academic,
1998.
Theoretical approaches to biological control. B. A Hawkins, H. W
Cornell, ed. Cambridge, Cambridge University Press, 1999.
Enhancing biological control. Habitat management to promote natural
enemies of agricultural pests. C. H Pickett, R. L Bugg, ed. Berkley,
CA, University of California Press, 1998.
Fabian D. Menalled and Richard G. Smith
Department of Land Resources and
Environmental Sciences
Montana State University
Bozeman, Montana
Environmental Entomology
Vol. 35, No. 4, August 2006, Page 1137
