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4 - Plant-mediated effects linking herbivory and pollination
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- By Judith L. Bronstein, University of Arizona, Travis E. Huxman, University of Arizona, Goggy Davidowitz, University of Arizona
- Edited by Takayuki Ohgushi, Kyoto University, Japan, Timothy P. Craig, University of Minnesota, Duluth, Peter W. Price, Northern Arizona University
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- Book:
- Ecological Communities
- Published online:
- 12 August 2009
- Print publication:
- 04 January 2007, pp 75-103
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Summary
Introduction
Over its lifetime, an individual plant must cope with a variety of challenges posed by other species. In fact, it may be interacting simultaneously with competitors, consumers, and a variety of mutualists, including pollinators, seed dispersers, and root symbionts. How the plant will fare in the presence of both beneficial and antagonistic species is at least in part a function of the resources it is able to devote to attracting and deterring them. Since resource availability is not unlimited, this sets up a situation in which allocation in the context of one set of interactions (such as attracting and rewarding mutualists) may force a trade-off with allocation in the context of another (such as defending against antagonists). While these trade-offs are well known, the vast majority of studies of interspecific interactions nevertheless focus on a single kind of interaction at a time. Hence, we know remarkably little about the nature and consequences of interactions among interactions experienced by a single organism.
One notable exception involves the topic of this chapter, interactions between herbivory and pollination. The literature on the ways in which herbivory alters pollination rates and hence reproductive success has grown rapidly in recent years. The large communities of researchers who focus on herbivory and on pollination now clearly recognize that they are not independent (Strauss 1997, Strauss and Armbruster 1997, Adler and Bronstein 2004, Irwin et al. 2004; see also Chapter 7, this volume).
16 - Coevolutionary Dynamics and the Conservation of Mutualisms
- Edited by Régis Ferrière, Ecole Normale Supérieure, Paris, Ulf Dieckmann, International Institute for Applied Systems Analysis, Austria, Denis Couvet, Muséum National d'Histoire Naturelle, Paris
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- Book:
- Evolutionary Conservation Biology
- Published online:
- 15 August 2009
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- 10 June 2004, pp 305-326
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Summary
Introduction
The vast majority of studies in conservation biology focus on a single species at a time. However, many of the anthropogenic threats that species face occur via disrupted or enhanced interactions with other organisms. According to one recent analysis, interactions with introduced species, such as predators, parasites, and pathogens, are the eighth leading cause of species endangerment worldwide; they are the primary cause of endangerment in Hawaii and Puerto Rico (Czech and Krausman 1997). Altering interactions not only has ecological effects, but also it can generate selective pressures and evolutionary responses, which may either favor or disfavor the evolutionary persistence of species and interactions. An increased focus on interspecific interactions will thus enlighten our efforts to conserve species and, more pointedly, our ability to understand when species will and will not respond evolutionarily to conservation threats. Such a focus is also critical for efforts to conserve communities as units, because interactions are the crucial and poorly understood link between threatened species and threatened species assemblages.
Different types of interspecific interactions are subject to, and generate, some-what different ecological and evolutionary threats. Predator and pathogen introductions can lead to reduction, local exclusion, or extinction of native species (Savidge 1987; Schofield 1989; Kinzie 1992; Steadman 1995; Louda et al. 1997). Rapid evolution in the enemies and/or the victims may also result (Dwyer et al. 1990; Singer and Thomas 1996; Carroll et al. 1998).
3 - Multitrophic/multispecies mutualistic interactions: the role of non-mutualists in shaping and mediating mutualisms
- Edited by Teja Tscharntke, Georg-August-Universität, Göttingen, Germany, Bradford A. Hawkins, University of California, Irvine
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- Book:
- Multitrophic Level Interactions
- Published online:
- 08 August 2009
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- 21 March 2002, pp 44-66
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Summary
Introduction
Off the coast of Massachusetts (USA), the hermit crab Pagurus longicarpus is often found carrying a colonial hydroid, Hydractinia, on its shell. In some situations, this interaction is clearly mutualistic: hermit crabs transport hydroids to rich feeding sites, and hydroids in turn deter larger, damaging organisms from colonizing hermit crab shells. The outcome of this interaction shifts away from mutualism, however, under other ecological conditions. The hydroid tends to be positively associated with a burrowing marine worm that weakens hermit crab shells to the point where they are easily crushed by predatory blue crabs (Callinectes sapidus). The nature of the hermit crab–hydroid association thus varies depending on which other species are present, shifting from mutualism (when blue crabs and/or worms are scarce), to commensalism, to antagonism (Buckley and Ebersole, 1994).
In most introductory biology textbooks, mutualism is defined as an association between organisms of two species in which both species benefit (e.g., Starr and Taggart, 1998; Tobin and Dusheck, 1998; Krogh, 2000). However, the hermit crab–hydroid interaction clearly demonstrates that at least some mutualisms can only be understood within a broader community context. The influence of other species and other trophic levels on mutualism has received curiously little attention, particularly in contrast to other types of interactions (see Barbosa and Letourneau, 1988; Cardé and Bell, 1995; Barbosa and Benrey, 1998; Barbosa and Wratten, 1998; Olff et al., 1999).