Meeting Abstract
Amblypygids are a charismatic group of arachnids that possess a unique pair of ‘raptorial’ pedipalps hypothesised to primarily function in prey capture. Little is known regarding intraspecific shape variation within these structures and potential underlying causes, however. A role during courtship and male conflict has also been hypothesised, and sexual selection may therefore contribute to shape change, alongside other environmental factors such as climate zone. This study aims to quantify the contribution of ontogeny, sexual dimorphism and environment to shape change within the raptorial pedipalps of Damon variegatus (n=96). Linear appendicular measures were regressed against body length using Type-II regression, and sex differences between slopes tested using the ‘smatr’ package in R. 2D geometric morphometrics was carried out on photographed specimens in MorphoJ. Pedipalp tibia length scaled to body size with significant positive allometry (b=1.822 p<0.001 r2= 0.874), yet showed no significant sexual dimorphism (SD). GMM revealed previously undetected SD in pedipalp shape in the tibia segment (p=0.0463), but no significant SD was found in the femur. Significant morphological disparity is also seen in both the tibia and femur between specimens from different climatic zones across Africa. Our results support multiple functions for the pedipalp; significant SD in tibia shape suggests sexual selection as a potential driving factor (either in courtship or male-male confrontation). Yet morphological disparity due to climate conditions also highlights factors other than sexual selection may be acting on pedipalp shape, for example, prey type.
