Meeting Abstract
Orb-weaving spiders have long been recognized to show substantial variation in body size, both within and between species. Within species, orb-weavers exhibit one of the most extreme examples of sexual size dimorphism in the animal kingdom, with females often orders of magnitude longer and more massive than conspecific males. Although inter- and intraspecific variation in orb-weaving spider body size is a well-studied phenomenon, body shape variation – and the potential role of allometric influences on body shape – remain largely unexplored. Here, we use geometric morphometric methods to quantify differences in carapace shape among members of the speciose, cosmopolitan orb-weaving spider family Araneidae, and test several hypotheses concerning the evolution of shape and size dimorphism in araneids. We find that males and females occupy distinct yet overlapping volumes of morphospace, with males generally having broader carapaces and more pronounced head regions than congeneric females. Although shape disparity is not significantly different between adult males and females, female carapace shape exhibits significant phylogenetic signal whereas male shape does not, perhaps indicating that male shape is less constrained evolutionarily. We discuss results as they relate to feeding habits, vagility, and fecundity differences between the sexes.
