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Chapter Two - Natural selection for anti-herbivore plant secondary metabolites
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- By Julianne M. O’Reilly-Wapstra, School of Plant Science, University of Tasmania, Brad M. Potts, School of Plant Science, University of Tasmania, Clare McArthur, School of Biological Sciences, University of Sydney
- Edited by Glenn R. Iason, Marcel Dicke, Wageningen Universiteit, The Netherlands, Susan E. Hartley, University of York
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- Book:
- The Ecology of Plant Secondary Metabolites
- Published online:
- 05 August 2012
- Print publication:
- 19 April 2012, pp 10-33
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Summary
Introduction
Since the seminal papers of Fraenkel (1959) and Ehrlich and Raven (1964), much research has demonstrated the role of plant secondary metabolites (PSMs) as defence mechanisms against invertebrate and vertebrate herbivory. These metabolites can act directly on the herbivore as toxins (Theis & Lerdau, 2003; Gershenzon & Dudareva, 2007), digestibility reducers (Ayres et al., 1997; De Gabriel et al., 2009) and deterrents (Pass & Foley, 2000), and they can also act indirectly by, for example, attracting natural enemies of the herbivore (Dicke, 2009). The idea that the herbivores themselves are acting as selective agents on these PSMs has existed since it was first noted that these compounds may serve as anti-herbivore traits, and in some systems it is clear that herbivores may act as agents of natural selection on some specific PSMs (Simms & Rausher, 1989; Mauricio & Rausher, 1997; Stinchcombe & Rausher, 2001; Agrawal, 2005). However, in most systems there is still a dearth of evidence addressing this question, particularly in light of the vast number of herbivores that attack a single plant species across its entire life and the array of PSMs that are expressed in a plant species. Are all of these herbivores agents of selection and have all PSMs evolved because of the selective pressures by the herbivores, or are PSMs driven by selection from other pressures such as abiotic factors (Close & McArthur, 2002)? Knowing the answer to these questions is important when attempting to understand what is driving population divergence within species and the evolution and change in PSMs.
For selection to occur there must be additive genetic-based variability in herbivory within plant populations. This herbivory must correlate with additive genetic-based variation in plant defensive traits, and herbivory must affect plant fitness (see Box 2.1). Key papers in the late 1980s through to the late 1990s clearly demonstrated the evolutionary impact that invertebrate herbivores were having on plant chemical defences in some systems (Rausher & Simms, 1989; Simms & Rausher, 1992; Rausher, 1993; Mauricio & Rausher, 1997; Juenger & Bergelson, 1998).
Chapter Fourteen - From genes to ecosystems
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- By Joseph K. Bailey, Department of Ecology and Evolutionary Biology, University of Tennessee, Jennifer A. Schweitzer, Department of Ecology and Evolutionary Biology, University of Tennessee, Francisco Úbeda, Department of Ecology and Evolutionary Biology, University of Tennessee, Benjamin M. Fitzpatrick, Department of Ecology and Evolutionary Biology, University of Tennessee, Mark A. Genung, Department of Ecology and Evolutionary Biology, University of Tennessee, Clara C. Pregitzer, Department of Ecology and Evolutionary Biology, University of Tennessee, Matthew Zinkgraf, Department of Biological Sciences, Northern Arizona University, Thomas G. Whitham, Department of Biological Sciences, Northern Arizona University, Arthur Keith, Department of Biological Sciences, Northern Arizona University, Julianne M. O’Reilly-Wapstra, Bradley M. Potts, School of Plant Science, University of Tasmania, Brian J. Rehill, Department of Chemistry, US Naval Academy, Carri J. LeRoy, Environmental Studies Program, The Evergreen State College, Dylan G. Fischer, Environmental Studies Program, The Evergreen State College
- Edited by Glenn R. Iason, Marcel Dicke, Wageningen Universiteit, The Netherlands, Susan E. Hartley, University of York
-
- Book:
- The Ecology of Plant Secondary Metabolites
- Published online:
- 05 August 2012
- Print publication:
- 19 April 2012, pp 269-286
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- Chapter
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Summary
Introduction
Relatively little is understood about the extent to which evolution in one species can result in changes to associated communities and ecosystems, the potential mechanisms responsible for those changes (genetic drift, gene flow or natural selection), the phenotypes or candidate genes that may link ecological and evolutionary dynamics, or the role of rapid evolution and feedbacks. However, linking genes and ecosystems in this manner is fundamental to placing community structure and ecosystem function in an evolutionary framework. This is not an easy endeavour as the field of community genetics is multi-disciplinary (Whitham et al., 2006), and ecological and evolutionary dynamics occur at different spatial and temporal scales. Recent reviews show that plant genetic variation can have extended consequences at the community and ecosystem level (extended phenotype; Whitham et al., 2003) affecting arthropod diversity, soil microbial communities, trophic interactions, carbon dynamics and soil nitrogen availability (Whitham et al., 2006; Johnson & Stinchcombe, 2007; Hughes et al., 2008; Bailey et al., 2009a). Its effects are not limited to single systems or even foundation species, but are common across broadly distributed plant and animal systems, and can have effects at the community and ecosystem level of similar magnitude to traditional ecological factors, such as differences among species (Bailey et al., 2009a, b).
Theory in the fields of community genetics (Shuster et al., 2006; Whitham et al., 2006) and co-evolution (Thompson, 2005) also supports the connection between evolutionary and ecological dynamics (Johnson et al., 2009). Multiple investigators argue that community and ecosystem phenotypes represent complex traits related to variation in the fitness consequences of inter-specific indirect genetic effects (IIGEs) (Thompson, 2005; Shuster et al., 2006; Whitham et al., 2006; Tetard-Jones et al., 2007). In their most basic form, IIGEs occur when the genotype of one individual affects the phenotype and fitness of an associated individual of a different species (Moore et al.,1997; Agrawal et al., 2001; Shuster et al., 2006; Wade, 2007). Such interactions are important in the geographic mosaic theory of co-evolution (Thompson, 2005), the development of community heritability (Shuster et al., 2006) and non-additive responses of community structure, biodiversity and ecosystem function (Bailey et al., 2009a). Empirical evidence for the effects of plant genetic variation on communities and ecosystems, paired with growing theoretical models explaining evolutionary mechanisms for these results, provides a solid foundation for understanding how evolutionary processes, such as drift and selection, may affect community structure and ecosystem function.