Diet-induced covariation between architectural and physicochemical plasticity in an extended phenotype

Abstract

The adaptive benefits of extended phenotypic plasticity are imprecisely defined due to a paucity of experiments examining traits that are manipulable and measurable across environments. Spider webs are often used as models to explore the adaptive benefits of variations in extended phenotypes across environments. Nonetheless, our understanding of the adaptive nature of the plastic responses of spider webs is impeded when web architectures and silk physicochemical properties appear to co-vary. An opportunity to examine this co-variation is presented by modifying prey items while measuring web architectures and silk physiochemical properties. Here, we performed two experiments to assess the nature of the association between web architectures and gluey silk properties when the orb web spider Argiope keyserlingi was fed a diet that varied in either mass and energy or prey size and feeding frequency. We found web architectures and gluey silk physicochemical properties to co-vary across treatments in both experiments. Specifically, web capture area co-varied with gluey droplet morphometrics, thread stickiness and salt concentrations when prey mass and energy were manipulated, and spiral spacing co-varied with gluey silk salt concentrations when prey size and feeding frequency were manipulated. We explained our results as A. keyserlingi plastically shifting its foraging strategy as multiple prey parameters simultaneously varied. We confirmed and extended previous work by showing that spiders use a variety of prey cues to concurrently adjust web and silk traits across different feeding regimes.

Indirect effects on fitness between individuals that have never met via an extended phenotype

“…Additionally, organisms may alter the environment by constructing some structure in it, such as a spider's web (Blamires et al . ,b), or leave scent cues to be detected by others (Cisterne et al . ).…”

Indirect effects on fitness between individuals that have never met via an extended phenotype

“…Many species hold territories that they may modify, for instance by digging out burrows, building nests or caching resources within them. Additionally, organisms may alter the environment by constructing some structure in it, such as a spider’s web (Blamires et al 2017a, b). Therefore, there is the potential for effects mediated by these extended phenotypes to be widespread throughout the natural world, yet our study is the first to quantify influences on life-history traits and fitness of other individuals mediated through an extended phenotype.…”

Orb-weaving spiders show a correlated syndrome of morphology and web structure in the wild

“…Causes and consequences for this consistent among-individual variation has been the source of great interest, especially within the last 20 years (Koolhaas et al 1999; Dall et al 2004; Réale et al 2007; Bell et al 2009; Stamps and Groothuis 2010). However, plasticity and consistency of extended phenotypes is not extensively documented (Venner et al 2000; Blamires 2010; Dirienzo and Montiglio 2016; Montiglio and DiRienzo 2016; Blamires, Hasemore, et al 2017; Blamires, Martens, et al 2017). Furthermore, the expression of extended phenotypes may covary with other repeatably expressed traits such as behaviours, or more stable straits such as morphology, but again this is not often documented (Dirienzo and Montiglio 2016; Montiglio and DiRienzo 2016).…”