Fitness consequences of plasticity in an extended phenotype

Abstract

Like regular phenotypes, extended phenotypes have demonstrable fitness advantages and their properties may vary plastically across environments. However, the fitness advantages of plasticity are only known for a select few extended phenotypes. It is known that the form and functions of spider orb webs can be manipulated by laboratory experiments. For instance, the physical and chemical properties of the spiral and gluey silks vary in property as protein intake varies. Orb web spiders thus represent good models for extended phenotypic plasticity studies. We performed experiments manipulating the protein intake of two vertically aligned orb web building spiders to determine whether variations in the chemical and physical properties of their spiral and gluey silk affect prey retention in their webs. We found in both spider species that individuals deprived of protein had a greater gluey silk glycoprotein core volume, and this correlated strongly with spiral thread stickiness and increased prey retention by the webs. Moreover, we found strong positive correlations between glue droplet volume and glycoprotein core volume for spiders in the protein-deprived treatment, but weaker correlations for protein-fed spiders. We interpreted these findings as the spiders investing more in glycoprotein when nutrient deprived. We attribute the associated increase in prey retention capacity as a fitness consequence of plasticity in the spiral properties.

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.…”

High contrast yellow mosaic patterns are prey attractants for orb‐weaving spiders

“…They are sit‐and‐wait foragers that rely on a range of strategies to acquire prey. These strategies include modifying the architecture of the web in response to fluctuating prey availability (Blamires, ; Blamires, Martens, & Kasumovic, ; Blamires & Tso, ; Heiling & Herberstein, ; Sandoval, ; Schneider & Vollrath, ), and exploiting different sensory channels to attract prey to the vicinity of the web, for instance by adding odours (Henneken, Goodger, Jones, & Elgar, ), colours (Craig, Weber, & Bernard, ; Hsiung, Justyn, Blackledge, & Shawkey, ), silken decorations (Tan et al, ; Walter & Elgar, ; Yeh, Blamires, Liao, & Tso, ) or prey remains (Bjorkman‐Chiswell et al, ; Tan & Li, ) to their webs, as well as conspicuous colour patterns on the body (Peng, Blamires, Agnarsson, Lin, & Tso, ; Tso, Lin, & Yang, ). There is remarkable variation in the colour patterns of web‐building spiders, and the commonly seen yellow or orange mosaic pattern on the ventral surface of orb‐weaver spiders can serve as visual lures to enhance foraging success (Blamires et al, ; Chuang, Yang, & Tso, ; Liao, Liao, Blamires, & Tso, ; Tso, Liao, & Huang, ; Tso, Tai, Ku, Kuo, & Yang, ; see also White & Kemp, for a review).…”