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Unformatted text preview: 3207 INTRODUCTION Animals may alter phenotypic form or function in response to changing environmental conditions, a phenomenon called phenotypic plasticity (Whitman and Agrawal, 2009; Auld et al., 2010). Plastic phenotypes are depicted by reaction norms or analyses of variation such as ANOVA and related procedures (Garland and Kelly, 2006; Whitman and Agrawal, 2009). Phenotypes extended beyond the organism, so-called extended phenotypes, are changeable within and among individuals, populations or clades (Dawkins, 1982). Extended phenotypes are complex because multiple factors influence phenotypic expression (Schaedelin and Taborsky, 2009). Additionally, extended phenotypes not only adapt to the demands of the environment, they interact with it, modify it and gain feedback from it, thereby creating phenotype–environment interactions that flow through generations (Lehmann, 2008). Owing to the interactions of multiple traits (Blanckenhorn, 1998), the complexity of the biological feedback mechanisms (Lehmann, 2008), and the interactive complexities of the various costs and limitations of plasticity (Auld et al., 2010), analyses of extended phenotypes are complex (Schaedelin and Taborsky, 2009). For analytical clarity, therefore, it is vital that studies investigating extended phenotypic plasticity minimize the multitudinous environmental effects and control the potentially interactive factors. The orb web is a conspicuous depiction of the physiological status and foraging stratagem of a spider (Heiling and Herberstein, 2000) and thus can be considered an extension of the spider phenotype (Craig, 2003). Orb-web architectural design is evolutionarily unstable, having been significantly modified over time in adaptation to selective challenges (Blackledge et al., 2009). Orb-web architecture has additionally evolved considerable plasticity (Heiling and Herberstein, 2000; Craig, 2003). Orb-web-building spiders, as a result, are exceptionally good model organisms for studying plasticity in extended phenotypes. Nevertheless, experimental determination of the environmental influences on orb-web plasticity is extremely complex. Firstly, specific architectural parameters respond differently to stimuli. For example, the capture area, web shape, symmetry, number of capture threads, mesh size (the distance between capture threads), the number of radial threads, the size and shape of decorations and silk properties may respond differently to various biotic and abiotic stimuli (Schneider and Vollrath, 1998; Heiling and Herberstein, 2000; Tso et al., 2005; Tso et al., 2007; Mayntz et al., 2009). Secondly, the nature of the stimuli inducing plasticity is multitudinous with prey type, prey abundance, prey nutrients, temperature, water availability, habitat complexity, predation pressure and web vibrations implicit in inducing plastic responses in orb spider webs (Vollrath et al., 1997; Herberstein et al., 2000a; Tso et al., 2005; Tso et al., 2007; Blamires et al., 2009;al....
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- Spring '11
- Ecology, cricket, Prey, Spider web, Sean J. Blamires