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Andrew Roberts
Faculty
The Ohio State University
Evolution Ecology and Organismal Biology
Newark, OH USA
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| Chemical communication in Schizocosa ocreata (Hentz): a reassessment. |
| Author(s) |
George W Uetz, Andrea Orton, Trisha Myers, Andrew Roberts |
| Info |
Talk category:
Behavior |
| Abstract |
Chemical communication is an important part of the mating process in the wolf spider Schizocosa ocreata (Hentz 1844), as cues associated with female silk are sufficient to elicit courtship from males. However, several questions arise about the role of chemical cues and the nature of chemical communication, which have not been studied in depth. We examined how both male and female S. ocreata wolf spiders respond to silk-borne, airborne and cuticular hydrocarbon (CHC) cues from members of either sex. Not surprisingly, males spent significantly more time on female silk. Females spent significantly less time on female silk. However, there were no significant differences for either sex between time on male silk vs. a control (filter paper, no silk). Males and females showed no significant directional response to airborne (olfactory) chemical cues from either sex, but males displayed courtship behaviors more often and at higher rates in the presence of airborne cues from females. Males responded with courtship to filter paper impregnated with cuticular hydrocarbon (CHC) cues of adult females, as well as female exuviae. Comparison of rates of male courtship behaviors exhibited in response to chemical cues from females suggest that silk-borne and CHC cues elicit higher rates of male signaling than airborne cues, but the latter may stimulate courtship at a distance. These data suggest that chemical communication in this species is unidirectional and female-originated, but more complex than previously believed, as multiple sources of chemical cues may be involved in stimulating male courtship. |
| Reproductive output under threat of predation in the wolf spider, Schizocosa ocreata (Hentz) |
| Author(s) |
Zeynep Benderlioglu, George Keeney, Andrew Roberts |
| Info |
Talk category:
Behavior |
| Abstract |
Exposure to environmental and genetic stressors during development has adverse consequences on physical growth, physiology, and behavior of individuals. One common environmental stressor is exposure to predators. Nonhuman animals have evolved adaptive mechanisms to avoid being eaten while optimizing reproductive function during predation risk. The current project investigates maternal exposure to predation risk and reproductive outcome in the wolf spider, Schizocosa ocreata (Araneae: Lycosidae). Mature S. ocreata females were either maintained in standard laboratory conditions (Non-Stressed; NS), or with exposure to silk and chemical cues from the generalist wolf spider predator Hogna helluo (Araneae: Lycosidae) for 12 days after mating (Hogna-Stressed; HS). Reproductive behaviors were assessed regarding eggsac production and clutch size. Results show that HS females had less variability in clutch size compared to NS females and that clutch size increased marginally. Whereas none of the HS females produced an eggsac during the 12-day stress period, NS females did so as early as 2 days after mating. Similarly, none of the HS females dropped an eggsac before reaching the minimum incubation period (28 days), whereas 50% of NS females did. All but one female in each group produced at least a second eggsac from the single mating trial. However, only those from HS females resulted in surviving offspring. Our results suggest that exposure to predation risk during egg development increases reproductive performance in S. ocreata and is associated with enhanced fitness as evidenced by increased clutch size and offspring survival. |
| Evidence for the role of experience and social density on eavesdropping and social facilitation of courtship in male Schizocosa ocreata wolf spiders (Lycosidae) |
| Author(s) |
David L Clark, Andrew Roberts, Corrina Kizer, Shira Gordan, George W Uetz |
| Info |
Talk category:
Behavior |
| Abstract |
Male spiders might reduce costs of finding females by “eavesdropping” and initiating sexual displays whenever male courtship is detected (i.e., social facilitation). A previous study found no evidence for eavesdropping in Schizocosa ocreata (Hentz), but involved spiders that matured in lab isolation (without exposure to behavior of adult conspecifics). In this study, males collected from the field as adults demonstrated behavior consistent with eavesdropping, i.e. increased interactive and courtship behaviors during and after video playback of a courting male stimulus. In contrast to previous findings, field-collected males showed a significantly longer duration of interactive behaviors and significantly more bouts of courtship activity when the video male stimulus was present on the video screen. Courtship rates of focal males were positively correlated with rates of courtship in video stimuli. Choice tests with two video screens showed that males recognize differences in male behavior, and respond to video stimuli of courting male wolf spiders more often and for a longer time than walking males or an empty leaf litter background (no spider). Additional studies with both live males and video playback showed that males exhibited significantly more time in courtship displays when presented with 2-3 additional males or male video stimuli simultaneously. Male responses to vibration signals from other males also varied with the presence/absence of female silk. Together, these findings suggest that experience arising from field exposure to adult conspecifics, along with additional variables such as competitor density and female chemical cues may impact male eavesdropping behavior and social facilitation. |
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