7.2 The real deal?: behavioral mimicry in hymenoptera  (Page 4/7)

In all of the examples discussed above regarding this mimetic behavior, aggressive mimicry is elucidated. In this form of mimicry, a predator or parasite imitates certain characteristics and attributes of the host in order to avoid detection.

Female mimicry and sexual success

Another topic of much interest within the context of mimicry and behavior is how the sex of organisms affects their sexual and reproductive success. This has been widely studied, and has become important with regard to mimicry because examples of conspecific gender mimicry have evolutionarily arisen as a means of optimizing sexual success.

One very interesting example of this conspecific gender mimicry occurs in the parasitic wasp species, Cotesia rubecula ( [link] ; Ayasse et al. 2001, Field&Keller 1993). This species is polygynous, and therefore, males mate with more than one female. This causes competition to arise between males as they vie for female mates, and thus, behavioral adaptations evolutionarily developed as a means to address this competition. One such adaptation that has impacted individual C. rubecula male sexual success is female mimicry. In this species, the majority of the females mate only once. Occasionally, if enticed, they will mate again in the post-copulatory period. During this period, the first male to mate becomes very protective, and has the desire to ensure that the female does not mate with another rival male. This will increase his personal reproductive success by maximizing the chances that his genes propagate. This mate-guarding behavior has been observed by Field and Keller (1993). In laboratory observations of C. rubecula , the first male to mate mimics a female’s receptive mating position upon being approached by a rival male either before, during, or immediately after copulation. This, in combination with the female’s sex pheromones being transferred onto the first mated male, usually distracts the rival male into futile attempts to mate with the mimic, during which time the actual female becomes unresponsive to post-copulatory advances (behavior and outcome pictured and explained in detail in [link] ). Thus, female mimicry serves as a method of mate-guarding behavior in Cotesia rubecula , and directly increases the sexual and reproductive success of males (Ayasse et al. 2001, Field&Keller 1993).

A genus of army ants, Eciton spp. , also exhibits female mimicry, but rather than mimicking female posture and sex pheromones, these male ants anatomically mimic their female counterparts (Ayasse et al. 2001). Worker males, who are not reproductively capable, have the ability to choose which male enters the colony and inseminates the queen. Therefore, this audition per se, has caused an evolutionary shift towards larger males that resemble queen shape and morphology. These reproductive males also have exocrine glands located on certain parts of their bodies similar to where they lie on the queen, further developing the anatomical female mimicry (Ayasse et al. 2001).

Reproductive strategies are also influenced by chemical mimicry in the tropical ant species, Cardiocondyla obscurior . Winged males exhibit conspecific female mimicry in this ant species (Anderson et al. 2003, Howard&Blomquist 2005). Wingless males are aggressive by nature due to competition for mates. However, by mimicking the cuticular hydrocarbon profiles of queens, winged males are able to court virgin queens without being attacked by aggressive wingless males. As such, wingless males also falsely court these winged males. Since both male species can reproduce with females, this female chemical mimicry is taken into a behavioral evolutionary context when considering the two very different reproductive strategies employed by males (Anderson et al. 2003, Howard&Blomquist 2005). Why do winged males get off the hook from attack from wingless males, especially since they are stiffer competition for mates? Anderson et al developed a mathematical model to answer this question (2003). Because winged males chemically resemble females, wingless males are subdued because letting winged male imposters live has been overall less costly than accidentally killing a virgin queen. Therefore, this explicates why chemical female mimicry has led to the development of two reproductive strategies that affect male C. obscurior sexual success (Anderson et al. 2003).