Meeting Abstract
40.2 Thursday, Jan. 5 Predation ability in the wolf spider Hogna helluo STEFFENSON, M.M.*; FORMANOWICZ, D.R.; University of Texas at Arlington; University of Texas at Arlington mmsteff@uta.edu
Spiders are classically used as an example of sexual size dimorphism among invertebrates. Theories postulated to explain the evolution of such gender differentiation include sexual selection for increased female size, differentiation in reproductive roles, and intersexual niche divergence to reduce competition in resource acquisition. Spiders of the genus Lycosidae are relatively unique among the Araneomorphae in that the degree of sexual size dimorphism is greatly reduced, but is however still present. Genders may also exhibit behavioral foraging contrasts. Male wolf spiders tend to wander more while females are more sedentary. Such morphological and behavioral dichotomies among sexes may result in differential predation success. The objective of this study was to identify differences in predation ability among gender groups in Hogna helluo (a cursorial Lycosid with an extensive geographical range), as well as to examine dissimilarities in morphology and behavior associated with prey capture. Spiders were captured by headlighting in local parks after dusk. Males, gravid females, and non-gravid females were introduced into experimental chambers with several levels of prey density to identify differences in foraging strategies and predation aptitudes. Morphological variation was examined using digital microscopy. Preliminary analysis indicates that morphological differentiation exists between males and females, but not between gravid and non-gravid females. At low prey densities, no differences in predation ability were detected. However, at higher cricket densities, gravid females captured the highest proportion of prey available, males captured the lowest proportion, and non-gravid females fell somewhere between the two. Results indicate that gravid females may be capturing higher proportions of prey due to the physiological consequences of offspring production.
