Sex-Specific Foraging Behaviours and Growth Rates in Juveniles Contribute to the Development of Extreme Sexual Size Dimorphism in a Spider~!2010-03-14~!2010-05-31~!2010-08-13~!

Abstract

Extreme sexual size dimorphism (SSD) in temperate species is expected to be proximally caused, at least partially, by sex-specific growth rates due to the limited time available for growth and reproduction. Hence sex-specific foraging strategies are predicted to mediate differential growth rates. However, little is known about how sex differences in foraging behaviour and growth trajectories relate to the expression of pronounced SSD. Here we tested for sex-specific foraging strategies and growth rates in juveniles of the highly size dimorphic orb-web spider Argiope aurantia under natural conditions. In a number of web sites, we estimated web height, web size (size of the prey capture area), mesh size, stabilimentum (web decoration) size and length, vegetation density and prey availability. Over four days in the field we also measured spider growth and web site tenacity. Independently of body size, females exhibited faster growth rate than males. When body size and condition were controlled for, we found that females built larger webs, and at sites with greater prey availability compared to males. Males built webs with significantly larger and longer stabilimenta independent of web size. These results indicate that extreme female-biased SSD in A. aurantia is at least partially the result of sex-specific growth rates already in early juvenile stages mediated by sex-specific web design and placement to allow for greater foraging success of females compared to males. We discuss these findings in the context of SSD evolution, and consider whether the sex-specific behaviours detected are more likely consequences or causes of the evolution of extreme SSD.

Phylogeny suggests nondirectional and isometric evolution of sexual size dimorphism in argiopine spiders

“…There, female size declined with increased elevation whereas male size did not change; this pattern, however, did not hold true for all species. Inkpen and Foellmer () argued that sex‐specific foraging behaviors and growth rates resulted in the extreme female‐biased SSD in the black and yellow garden spider, Argiope aurantia . The authors demonstrated different foraging behaviors and hence prey availabilities for females, building larger webs, and for males, constructing more conspicuous web decorations, so called stabilimenta.…”

Sexual Size Dimorphism: Evolution and Perils of Extreme Phenotypes in Spiders

“…Gendered foraging strategies and differential growth rates are two additional natural selection drivers of size evolution. Whether they are proximate causes for SSD (61) or consequences of SSD is unclear. Females have higher nutritional requirements than males, which should lead to different foraging (web) biologies and developmental trajectories.…”

The interactions between habitat, sex, biomass and leaf traits of different willow (Salix) genotypes

“…It is well-known-almost a truism-that differences between sexes are common in nature and determine primary and secondary sex characters (Barrett and Hough 2013). Sexual dimorphism (SD) is observed in many organisms, such as humans, cervids (Geist and Bayer 2009), birds (Owens and Hartley 1998), spiders (Foellmer and Moya-Laraño 2007;Inkpen and Foellmer 2010) and other animals, while SD in plants is much less widely appreciated (Geber et al 1999). Meanwhile, focusing attention on the sex of plant specimens and the effects of the differences between the sexes may have significant ecological and practical significance.…”