Detection of predator cues alters mating tactics in male wolf spiders

Males of the wolf spider, Rabidosa punctulata, exhibit condition-dependent alternative mating tactics, whereby small, poor condition males engage in multimodal courtship while large, good condition males adopt a direct mount tactic that forgoes courtship. This study explores the possibility that tactic-specific costs can help explain this unintuitive pattern of mating tactic expression. Specifically, we hypothesize that courtship signaling is costly with respect to eavesdropping by predators and that males can alter their tactic expression based upon the perceived environmental predation risk. We test this by first examining the risk of predation associated with different mating tactics. We use a co-occurring predatory heterospecific, R. rabida as our predator. We found support for the prediction that courting R. punctulata males tended to be attacked more often than non-courting males, and the likelihood of being attacked was best predicted by courtship activity. Given this documented cost, we hypothesized that R. punctulata males would adjust their mating tactic based upon perceived predation risk. In a second experiment, we manipulated perceived predation risk by providing R. punctulata males with different female silk cues (conspecific; predatory heterospecific; conspecific + predatory heterospecific) and examined mating tactic expression. In support of our hypothesis, males were more likely to adopt the direct mount tactic in the presence of predatory heterospecific or mixed silk cues and were more likely to court in the presence of conspecific cues. These results support the hypothesis that the cost of predation from eavesdroppers may influence the evolution and expression of male alternative mating tactics in R. punctulata

Detection of predator cues alters mating tactics in male wolf spiders

Males of the wolf spider, Rabidosa punctulata, exhibit condition-dependent alternative mating tactics, whereby small, poor condition males engage in multimodal courtship while large, good condition males adopt a direct mount tactic that forgoes courtship. This study explores the possibility that tactic-specific costs can help explain this unintuitive pattern of mating tactic expression. Specifically, we hypothesize that courtship signaling is costly with respect to eavesdropping by predators and that males can alter their tactic expression based upon the perceived environmental predation risk. We test this by first examining the risk of predation associated with different mating tactics. We use a co-occurring predatory heterospecific, R. rabida as our predator. We found support for the prediction that courting R. punctulata males tended to be attacked more often than non-courting males, and the likelihood of being attacked was best predicted by courtship activity. Given this documented cost, we hypothesized that R. punctulata males would adjust their mating tactic based upon perceived predation risk. In a second experiment, we manipulated perceived predation risk by providing R. punctulata males with different female silk cues (conspecific; predatory heterospecific; conspecific + predatory heterospecific) and examined mating tactic expression. In support of our hypothesis, males were more likely to adopt the direct mount tactic in the presence of predatory heterospecific or mixed silk cues and were more likely to court in the presence of conspecific cues. These results support the hypothesis that the cost of predation from eavesdroppers may influence the evolution and expression of male alternative mating tactics in R. punctulata

The Complexities of Wolf Spider Communication Exploring Courtship Signal Function in \u3ci\u3eRabidosa rabida\u3c/i\u3e

Evidence of signal complexity is seemingly pervasive across animal communication systems. Exploring signal function may provide insight into how these displays evolved and are maintained. This dissertation examines the courtship signal function in a grassland wolf spider. Rabidosa rabida lives in an extremely complex environment, and males use complex displays incorporating both visual and seismic modalities. Using several approaches I provide insight into the content and efficacy of the various signal components, as well as how variation in these displays influence female mating decisions in isolation and combined. First, I manipulated male and female body condition using diet quantity manipulations and performed mate choice trials using females of each diet across two different age classes. Female mate choice decisions varied with diet and age. Overall, younger females were choosy, mating more often with good condition males, while older females mated indiscriminately. Next, to determine which signal components may be useful in female mate assessment, I explored the condition-dependence of the signal components and tested their efficacy by performing mate choice trials in environments that differed in modality transmission. Both visual and seismic components are condition-dependent, and are sufficient to maintain copulation success when detected in isolation. Thus, each signal component may serve as both a content- and efficacy-backup when facing variable sensory environments. Lastly, I manipulated both foreleg ornamentation and the seismic display, and presented them to females both in isolation and combined, to determine if and how variation in each component influences female mating decisions. Females were choosy based on the seismic display alone, and only discriminated males based on foreleg ornamentation when detected along with a seismic signal, suggesting an inter-signal interaction. Together, these experiments suggest that the sources of selection acting on male R. rabida are just as complex as the courtship displays used during mating interactions. The courtship signal components making up the display appear to function by maintaining both copulation success and mate assessment across a variety of environments encountered

Complex courtship displays facilitate male reproductive success and plasticity in signaling across variable environments

Effective signal transmission is essential for communication. In environments where signal transmission is highly variable, signalers may utilize complex signals, which incorporate multiple components and modalities, to maintain effective communication. Male Rabidosa rabida wolf spiders produce complex courtship signals, consisting of both visual and seismic components. We test the hypothesis that the complex signaling of R. rabida contributes to male reproductive success in variable signaling environments. We first examine the condition-dependence of ornamentation (a presumed visual signal) and seismic signal components and find that both may provide potentially redundant information on foraging history. Next, we assessed reproductive success across manipulated signaling environments that varied in the effectiveness of visual and/or seismic signal transmission. In environments where only one signal could be successfully transmitted (e.g., visual or seismic), pairs were still able to successfully copulate. Additionally, we found that males altered their courtship display depending on the current signaling environment. Specifically, males reduced their use of a visual display component in signaling environments where visual signal transmission was ablated. Incorporating signals in multiple modalities not only enables R. rabida males to maintain copulation success across variable signaling environments, but it also enables males to adjust their composite courtship display to current signaling conditions [Current Zoology 57 (2): 175–186, 2011]

Enigmatic Ornamentation Eases Male Reliance on Courtship Performance for Mating Success

Female preferences are frequently invoked to explain the widespread occurrence of elaborate male ornaments, yet empirical data demonstrating such preferences are sometimes equivocal or even contradictory. In the wolf spider Schizocosa stridulans, despite evidence of strong female choice, prior research has been unable to link the conspicuous sexually dimorphic foreleg ornamentation of males to their mating success. We conducted three experiments aimed at determining the function of this previously enigmatic ornamentation. Our first two experiments used males with phenotypically modified foreleg phenotypes in simple and complex mating environments in order to examine the relationship between the presence/absence of ornamentation and male mating success. In both experiments, we found no relationship: courtship rate was the sole predictor of mating success. In a third experiment, we used males with naturally varying foreleg ornamentation in mating trials. Ornamentation was subsequently quantified and we again examined the factors influencing male mating success. As in our first two experiments, we found courtship rate to be a good predictor of mating success. Additionally, we discovered that foreleg ornamentation and courtship rate interact to influence male mating success. At low courtship rates, males with more foreleg ornamentation have a mating advantage, whereas at high courtship rates, males with less foreleg ornamentation have a mating advantage. We discuss several potential explanations for these results. In summary, we provide the first evidence of a benefit of foreleg ornamentation in male S. stridulans and suggest that this benefit is realized by the interaction between ornamentation and courtship rate

Octopamine levels relate to male mating tactic expression in the wolf spider \u3ci\u3eRabidosa punctulata\u3c/i\u3e

In the wolf spider Rabidosa punctulata, upon encountering a female, males use one of two distinct strategies: (1) they court the female in an attempt to elicit a mating, or (2) they engage in a direct-mount tactic that involves extensive grappling with the female until a mating is achieved. The latter tactic appears more sexually aggressive, and both tactics come with the risk of being cannibalized. We explored the physiological mechanisms underlying this behavioral variation by assessing the relationship between circulating levels of the biogenic amine octopamine (OA), a neuromodulator suggested to play a role in “fight or flight” responses of arthropods and male mating tactic expression. We predicted, and found support for, a relationship between OA levels and tactic expression, with males adopting the direct-mount tactic expressing higher OA levels than courting males. Male mating tactic and mass also showed a significant interaction, with a negative trend in direct-mounting males and no relationship in courting males. Males had considerably higher levels of OA circulating in their hemolymph than females and female OA level increased with female mass. Our experimental design cannot disentangle cause from effect, but our results are consistent with the hypothesis that OA plays a role in regulating mating tactic expression in R. punctulata

Courtship effort is a better predictor of mating success than ornamentation for male wolf spiders

Female mate choice decisions are often based on a variety of male characteristics, some of which may reflect male quality via condition-dependent trait expression. Here, we explore the condition dependence of a male secondary sexual trait in a wolf spider and examine its influence on female mate choice. In the wolf spider Schizocosa uetzi, mature males possess a multimodal courtship display (visual + seismic) in which they slowly raise and lower their dark colored forelegs. Foreleg color is highly variable among S. uetzi males with respect to both total amount and darkness. Using diet manipulations in conjunction with color quantifications, we demonstrate condition-dependent foreleg color. High-nutrient diet males had significantly higher body condition indices and possessed more and darker foreleg color than low-nutrient diet males. However, using multiple mate choice designs, we were unable to demonstrate a female preference for male foreleg color. Using both single and 2-choice mating designs as well as using females from a range of ages, we found that copulation success was consistently independent of male foreleg color. Instead, we found courtship intensity to be the only aspect of male courtship that influenced copulation success—males that copulated displayed more leg raises per second than those that did not copulate

Females Are Choosier in the Dark: Environment-Dependent Reliance on Courtship Components and Its Impact on Fitness

A broad understanding of multimodal courtship function necessitates knowledge of the potential information content of signal components, the efficacy of signal components in eliciting the appropriate receiver response, and the fitness consequences of mating decisions based upon various signal components. We present data addressing each of these requirements for the multimodal-signaling wolf spider, Schizocosa floridana Bryant. Using diet manipulations, we first demonstrate that both visual and seismic courtship signals are condition-dependent. Next, using high- and low-quantity diet individuals in mate choice trials across manipulated signaling environments, we demonstrate that the seismic signal is crucial for mating success and further show that female choosiness is environment-dependent. Females mated more with high diet males only in the absence of visual signals, showing no discrimination in the presence of visual signals. Finally, by quantifying the number of offspring produced by our mated females, we reveal that a female’s mating environment, in conjunction with her potential resource availability, influences her fitness—in environments in which females exerted choice, heavier females produced more offspring. Together, this comprehensive set of experiments demonstrates that female choosiness varies across environments, leading to direct fitness consequences

Octopamine Levels Relate to Male Mating Tactic Expression in the Wolf Spider Rabidosa punctulata

In the wolf spider Rabidosa punctulata, upon encountering a female, males use one of two distinct strategies: (1) they court the female in an attempt to elicit a mating, or (2) they engage in a direct-mount tactic that involves extensive grappling with the female until a mating is achieved. The latter tactic appears more sexually aggressive, and both tactics come with the risk of being cannibalized. We explored the physiological mechanisms underlying this behavioural variation by assessing the relationship between circulating levels of the biogenic amine octopamine (OA), a neuromodulator suggested to play a role in \u27fight or flight\u27 responses of arthropods and male mating tactic expression. We predicted, and found support for, a relationship between OA levels and tactic expression, with males adopting the direct-mount tactic expressing higher OA levels than courting males. Male mating tactic and mass also showed a significant interaction, with a negative trend in direct-mounting males and no relationship in courting males. Males had considerably higher levels of OA circulating in their haemolymph than females and female OA level increased with female mass. Our experimental design cannot disentangle cause from effect, but our results are consistent with the hypothesis that OA plays a role in regulating mating tactic expression in R.punctulata