Behavioral Ecology of Insect Parasitoids

Behavioral Ecology of Insect Parasitoids

Éric Wajnberg & Carlos Bernstein
Published in: Blackwell Publishing
Release Year: 2008
ISBN: 978-1-4051-6347-7
Edition: First Edition
File Size: 3 MB
File Type: pdf
Language: English

Description of Behavioral Ecology of

Insect Parasitoids

Parasitoids are fascinating insects, whose adult females lay their eggs in or on other insects. The parasitoid larvae develop by feeding on the host bodies, resulting in the death of the host. Parasitoids are found in nearly all terrestrial ecosystems and show a vast biological and ecological diversity and a wide array of specific adaptations, making them ideal subjects for comparative research. For their reproduction, they depend on finding and attacking hosts and, as a consequence, they are under strong natural selection to develop efficient host search and attack strategies, often through elaborate behavioral mechanisms. This makes these insects superb models for testing evolutionary hypotheses, also because a direct link exists between host search and attack behavior of a parasitoid and its fitness, as the number of hosts parasitized is proportional to the number of offspring produced. Further, since their reproduction results in the death of their hosts, parasitoids are often important factors in the natural control of insect populations, thus preventing insect pests. Certain species are mass-produced and released on a large scale to limit or suppress insect pests attacking different crops. ‘Biological control’, as this technique is known, can lead to a highly significant reduction in the use of toxic chemical pesticides, thus reducing the
impact on non-target organisms.
This book originated from the European scientific program ‘Behavioural Ecology of Insect Parasitoids’, financially supported by the European Science Foundation (ESF). Behavioral ecology is a scientific discipline that strives to understand animal behavior under natural conditions in evolutionary terms, i.e. by asking what the adaptive advantages of a particular behavior are. This is done by comparing the actual behavior of animals with predictions of theoretical models of how animals should behave so as to optimize their fitness, given a realistic set of constraints. The aim of the models, frequently expressed in mathematical terms, is to better define the questions and to help in designing experiments. Experimental work puts the hypothesis to the test and the differences between experimental results and theory help in identifying any weakness in our understanding. This suggests aspects of the problem that might have been overlooked and that would be subsequently incorporated into new models or tested in new experiments. The scope of behavioral ecology extends to the population level. Incorporating optimal behaviors and deviations from these archetypes, into models of population dynamics, allows increasing their realism by putting them on a firm evolutionary footing. In recent decades, this approach has been developed with ample success by using different animals (e.g. mammals, birds, fishes, and also insects).
Biological control has resulted both in remarkable successes and in definitive failures. Biological control programs follow in general an empirical approach and practitioners often have a limited understanding of the reasons for the different fates (success or otherwise) of control attempts. There is, as a consequence, a clear need to base pest control practices on a firm, formal scientific basis. As all living beings have been shaped by natural selection, evolutionary thinking is the key to the understanding of the workings of nature (‘Nothing in Biology makes sense except in the light of evolution,’ Dobzhansky (1973) The American Biology Teacher 35: 125–9), on which sound species management should be based. In parasitoids, parasitism behavior is central to the success of biological control, because the death of the host results from the production of progeny. In spite of this, the theoretical and experimental achievements in the understanding of the evolution of parasitoid behavior and life-history traits have been seldom put to use as a means of improving the efficacy of biological control programs. However, it has been successfully applied in the selection of the most promising candidates for release, in improving parasitoid mass rearing efficiency, and in the evaluation of success and failure of parasitoids as biocontrol
agents. As a consequence, in this volume, we combine the study of fundamental aspects of parasitoid behavior with a discussion of their possible consequences for the efficacy of selective pest control.
This book contains 18 chapters, each of them written by two distinguished specialists, covering virtually all the key aspects of parasitoid behavior and their relevance for efficient biological control programs. The first part presents current issues in the behavioral ecology of insect parasitoids. It starts with Chapter 1 linking optimal foraging behavior to efficient biological control. Chapter 2 proposes an accurate definition of fitness, how it translates in these particular insects, and how fitness should be estimated. Then, since behavioral ecology addresses the behavior of parasitoids under natural conditions, the same conditions under which biological control takes place, Chapter 3 contributes to the understanding of parasitoid decisionmaking under field situations. After Chapter 4 has addressed the important issue of competition between parasitoids and other species foraging for hosts at the same trophic level, Chapters 5 to 9 discuss the ‘classical’ questions of parasitoid behavior, namely responses to chemical cues for finding hosts (Chapter 5), the physiological mechanisms involved in behavioral decisions (Chapter 6), food searching strategies (Chapter 7), patch time allocation (Chapter 8), and competition between foraging females on patches of hosts (Chapter 9). Finally, Chapter 10 deals with potential risk assessment strategies adopted by these insects. 
The second part of the volume addresses the extension of the evolutionary approach of behavioral ecology to other related scientific questions. To start with, Chapter 11 looks at the consequences of parasitoid behavior in a multitrophic context. Then, Chapter 12 discusses sex ratio control and Chapter 13 considers the consequences of parasitoid behavioral ecology for population dynamics. Finally, Chapter 14 raises the potential link between parasitoid behavior and the development of resistance/virulence physiological mechanisms in host-parasitoid associations. Since a behavioral ecology approach of such tiny animals cannot be developed without the use of specific technical tools, the last section of the volume addresses some methodological issues, especially those developed for the study of insect parasitoids. Chapter 15 presents how state-dependent problems should be addressed, while Chapter 16 discusses more specifically Bayesian approaches. Finally, Chapter 17 presents how genetic algorithms can be used to find optimal behavioral decisions under different environmental conditions and Chapter 18 summarizes the most recent statistical methods that should be used for a sound analysis of behavioral data. We hope that this volume is timely and that it will foster research on the behavioral ecology of insect parasitoids and propose new and interesting avenues for future research. We hope that it will rapidly become an important reference for both scientists and students working on parasitoid biology and for everyone involved in using parasitoids in biological control programs.
We want to thank several referees that read and commented critically on one or more chapters. They include Pierre Bernhard, Carlos Bernstein, Jérôme Casas, Patrick Coquillard, Anne-Marie Cortesero, Christine Curty, René Feyereisen, Luc-Alain Giraldeau, Patsy Haccou, Thomas Hoffmeister, Mark Jervis, Finn Kjellberg, Nick Mills, Franco Pennacchio, Jean-Sébastien Pierre, Marylène Poirié, Odile Pons, Geneviève Prévost, Bernie Roitberg, Brigitte Tenhumberg, Jacques van Alphen, Minus van Baalen, Brad Vinson, and Éric Wajnberg. Much editing work has been done in order to homogenize the content of the book, but all information, results, and discussion provided in each chapter are under the single responsibility of their corresponding authors. We finally want to express our sincere thanks to the ESF and to the people at Blackwell Publishing for their efficient help and support in the production of this book.

Content of Behavioral Ecology of Insect Parasitoids

Part 1 Current issues in the behavioral ecology of insect
parasitoids 1
1 Optimal foraging behavior and efficient biological control methods 3
Nick J. Mills and Éric Wajnberg
2 Parasitoid fitness: from a simple idea to an intricate concept 31
Minus van Baalen and Lia Henrik
3 Parasitoid foraging and oviposition behavior in the field 51
George E. Heimpel and Jérôme Casas
4 Behavior influences whether intra-guild predation disrupts herbivore
suppression by parasitoids 71
William E. Snyder and Anthony R. Ives
5 Chemical and behavioral ecology in insect parasitoids: how to behave
optimally in a complex odorous environment 92
Monika Hilker and Jeremy McNeil
6 Parasitoid and host nutritional physiology in behavioral ecology 113
Michael R. Strand and Jérôme Casas
7 Food-searching in parasitoids: the dilemma of choosing between
‘immediate’ or future fitness gains 129
Carlos Bernstein and Mark Jervis
8 Information acquisition, information processing, and patch time
allocation in insect parasitoids 172
Jacques J.M. van Alphen and Carlos Bernstein
9 Competition and asymmetric wars of attrition in insect parasitoids 193
Patsy Haccou and Jacques J.M. van Alphen
10 Risk assessment and host exploitation strategies in insect parasitoids 212
Luc-Alain Giraldeau and Guy Boivin
Part 2 Extension of the behavioral ecology of insect
parasitoids to other fields 229
11 Multitrophic interactions and parasitoid behavioral ecology 231
Louise E.M. Vet and H. Charles J. Godfray
12 Parasitoid sex ratios and biological control 253
Paul J. Ode and Ian C.W. Hardy
13 Linking foraging and dynamics 292
Michael B. Bonsall and Carlos Bernstein
14 Linking behavioral ecology to the study of host resistance and parasitoid
counter-resistance 315
Alex R. Kraaijeveld and H. Charles J. Godfray
Part 3 Methodological issues in behavioral ecology 335
15 State-dependent problems for parasitoids: case studies and solutions 337
Bernard Roitberg and Pierre Bernhard
16 A Bayesian approach to optimal foraging in parasitoids 357
Jean-Sébastien Pierre and Richard F. Green
17 Finding optimal behaviors with genetic algorithms 384
Thomas S. Hoffmeister and Éric Wajnberg
18 Statistical tools for analyzing data on the behavioral ecology of insect
parasitoids 402
Éric Wajnberg and Patsy Haccou

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