Katherine L. Barry

Male mate choice: why sequential choice can make its evolution difficult

Male reproductive success is typically mate limited, which implies that males should rarely be choosy. On the other hand, females often vary greatly in their fecundity or other determinants of male reproductive success. There are two coexisting threads in the current literature on male mate choice: a number of studies emphasize that male mate choice has been underappreciated in the past, while another set reminds us that it nevertheless evolves less easily than female choice. Here we show that when mate choice is sequential rather than simultaneous (which is often the case for the mate-limited sex), male mate choice may fail to evolve even if there is large variation among fitness prospects offered by various females, and when mating is very costly. Our model is inspired by the mating system of the sexually cannibalistic praying mantid Pseudomantis albofimbriata. Males of this species do not stop approaching females that have turned to face them even though this female behaviour greatly increases the risk of being cannibalized. We show that low mate availability can override the effect of all other factors that select for male mate choice: rejecting a current mating opportunity in the hope of better future opportunities is then not easily selected for. We conclude that studies of mate choice should examine why individuals refuse to take advantage of every opportunity, instead of merely focusing on the fact that some opportunities are better than others. Our results also call for more rigorous empirical tests of mate choice.

Multimodal mate assessment by male praying mantids in a sexually cannibalistic mating system

The traditional view of sexual selection has been that of competing males and choosy females; however, more recently it has been recognized that males mayexhibit mate choice when females vary in quality and when males suffer costs associated with mating. Sexually cannibalistic mating systems provide an opportunitytoexaminemalematechoicefurther:thehighcostspotentiallyinvolvedinthematingprocess for males, as well as variation in female quality, predict male mate choice. We used the praying mantid Pseudomantis albo! mbriata to determine the effect of female body condition on male mate choice in a system with frequent precopulatory sexual cannibalism. Female body condition is positively correlated with fecundity and negatively correlated with the propensity to cannibalize, so we predicted males would strongly prefer females in good condition to maximize their reproductive potential. Results of our simultaneouschoicetestsshowedthatmalesusechemicalandvisualcuesformatelocationandassessment,and that theycan use eitherof these sensory modalities to distinguish and choose between females differing in body condition, with a signi! cant preference for good-condition females. However, surprisingly, males rarely rejected poor-condition females in the more ecologically relevant scenario of only one immediate potential mate and both sensory modes available to them, which may be explained by the strong scramble competition known for praying mantid systems. These results show that even when female quality varies and the cost of mating for males is substantial, male mate rejection does not always evolve. Crown Copyright ! 2010. Published on behalf of The Association for the Study of Animal Behaviour by Elsevier Ltd. All rights reserved.

Effects of female feeding regime in a sexually cannibalistic mantid: fecundity, cannibalism, and male response in Stagmomantis limbata (Mantodea)

1. Female feeding regime exhibited a cascade of effects on reproductive biology and behaviour in the mantid Stagmomantis limbata (Hahn).

Examinations of Female Pheromone Use in Two Praying Mantids, Stagmomantis limbata and Tenodera aridifolia sinensis (Mantodea: Mantidae)

ABSTRACT Female pheromones were examined in two species of praying mantids: Stagmomantis limbata Hahn and the Chinese mantid, Tenodera aridifolia sinensis Saussure. As in other mantids, females of both of these species are poor flyers or flightless, whereas males are flight-capable. Yet, they differ in ecology and biogeography, with the study population of S. limbata (native to Nearctic region) occurring at low density in desert habitat, and the study population of T. aridifolia sinensis (native to Indomalaya region) occurring at high density in humid woodlands. For both species, we designed field experiments to allow for the attraction of males via chemical signals while controlling for visual cues. Both species show evidence of female-emitted pheromones. In S. limbata, females in covered field cages attracted males, whereas large insects (cockroaches) in covered cages and covered empty cages failed to attract any males. In a second experiment with S. limbata, males were preferentially attracted to well-fed females over poorly-fed females, suggesting that pheromone emission is an “honest” signal of female receptivity in this species. Male arrivals in S. limbata were significantly clustered in the first few hours after sunrise. In T. aridifolia sinensis, covered females (female chemical cues) attracted more males than paired covered controls (empty), and attracted more males than uncovered conspecific males (male chemical and visual cues). Females in uncovered cages (female chemical and visual cues) attracted more males than covered females and more than uncovered controls (empty). This last result highlights the dual importance of chemical and visual information in mantid mating behavior. Female-emitted pheromones are certainly important in long-distance attraction in mantids, whereas visual cues and signals become important at shorter range.

Male mating behaviour reduces the risk of sexual cannibalism in an Australian praying mantid

In cases where sexual cannibalism represents a sexual conflict, we should expect to find male traits that reduce the risk of cannibalism. In fact, a wide variety of such traits have been proposed, including elaborate courtship displays, cautious approach behaviours, and opportunistic mating whilst a female is feeding. However, there is very little direct evidence that these behaviours actually reduce the risk of sexual cannibalism for males, and the evidence that does exist comes mainly from spider studies. In this study of Pseudomantis albofimbriata praying mantids we found evidence of various male behaviours that reduced the risk of sexual cannibalism. Most males attempted to avoid detection entirely and others moved in a slow and stealthy manner. We also observed five cases of opportunistic mating, but saw no evidence of any male courtship routine. It seems that mounting from the rear of a female or slowly approaching her from the front, allows many males to go unnoticed and, therefore, substantially reduces the risk of sexual cannibalism in this mating system. Interestingly, we could not identify any female traits that males use to assess the risk of sexual cannibalism. It may be that P. albofimbriata males use alternative means to assess these risks. The presence of these behavioural strategies by males suggests a net cost of being consumed, and that sexual cannibalism is likely to be a female strategy in this system.

Influence of female nutritional status on mating dynamics in a sexually cannibalistic praying mantid

The classical paradigm of sexual selection is that of advertising males and choosy females; however, male mate choice may be more common than previously thought. Unlike visual and acoustic cues, females rather than males usually emit long-distance chemical signals for mate attraction, thus providing an excellent opportunity to examine male mate choice further. Here, I used the sexually cannibalistic praying mantid Pseudomantis albofimbriata to determine the effect of female body condition on male mate choice via chemical cues in a natural scenario. Female body condition is positively correlated with fecundity and negatively correlated with the propensity to cannibalize in this system, so I predicted strong male mate choice for good-condition females to maximize male reproductive fitness. Results of field-based choice tests showed differential male attraction to good-condition females: all males were found on the cages of good-condition females and none on those of poor-condition females. In a second series of choice tests conducted in large field enclosures, I found that some poor-condition females attracted males in the absence of good-condition females, and that these females had significantly more eggs in their ovaries than the unattractive poor-condition females. Furthermore, when egg number was controlled but female body condition varied, males no longer had a significant preference for good-condition females. I therefore propose that the male preference for fecund females is a result of egg-bearing females producing a greater quantity/quality of pheromone than egg-free females, and that chemical cues are likely to be an honest indicator of female fecundity in this system.

A paternity advantage for speedy males? Sperm precedence patterns and female re-mating frequencies in a sexually cannibalistic praying mantid

Scramble competition polygyny is expected when females and/or resources are widely dispersed and not easily monopolized by males, or when there is an abundance of mates during an extremely restricted reproductive period. Additional factors such as first male sperm precedence or low female re-mating rate might further explain the propensity of males to engage in scramble competition. The sexually cannibalistic praying mantid Pseudomantis albofimbriata exhibits a polygynous mating system, where females exist in low-density populations and male competition manifests as the race to find females rather than as direct physical fighting. Here, we aim to determine whether there is a paternity advantage for the first-male to mate and/or a low frequency of female re-mating. First, we determined sperm precedence patterns in P. albofimbriata using the sterile male technique. Second, we tested the likelihood of female re-mating in P. albofimbriata by comparing the close-range approach behaviour and frequency of successful mating attempts for males when paired with virgin as opposed to recently mated females, and by comparing the frequency of long-distance male attraction between virgin and mated females. We found no paternity advantage for the first male to mate, rather a second male advantage. Although mated females were not rejected by males when approached from close-range, they were chemically unattractive to males searching from a distance. Since initial mate attraction in many praying mantids, including P. albofimbriata, is mediated via long-distance chemical communication, we believe the latter result is more ecologically relevant and therefore more important. These results suggest that the relatively low frequency of female re-mating observed in P. albofimbriata may be an additional factor driving scramble competition in this system.

Sexual signals for the colour-blind: cryptic female mantids signal quality through brightness

Summary Cryptic coloration may evolve in response to selective pressure imposed by predators, yet effective intraspecific communication may require some level of detectability. This creates a tension between the benefits of sexually selected visual traits and the predatory costs imposed by greater conspicuousness, and little is known about how this tension may be ameliorated in highly cryptic species. We explore these competing demands in the false garden mantid Pseudomantis albofimbriata, a colour-blind and seemingly cryptic insect. We use reflectance spectrometry and receptor-noise modelling to characterize the conspicuousness of mantid body regions in the visual systems of mates (mantids), as well as potential predators (birds) and prey (bees). We then use condition manipulation and conspecific choice tests to further explore the colour traits of interest. Based on visual modelling, we find that male mantids are inconspicuous to conspecifics, prey and predators – that is, they are chromatically and achromatically cryptic. In contrast, female mantids are chromatically cryptic to all potential receivers, but their abdomens are achromatically conspicuous. Our food manipulation experiment shows that females in good condition (and therefore with more eggs) have brighter abdomens than females in poor condition. Choice assays show male mantids are consistently attracted to females bearing brighter abdomens. Our results reveal brightness-mediated sexual signalling in a colour-blind and classically cryptic insect. By communicating in the only visual channel available to them, female mantids are conspicuously signalling their quality to mates, while potentially minimizing their conspicuousness to predators and prey. Furthermore, by signalling with only a single body region, female mantids are apparently using coincident disruptive coloration to further decrease detectability to potential eavesdroppers. Our data reveal a novel example of the way in which the trade-off between sexual selection for conspicuousness and natural selection for crypsis may be mediated in a visual signalling system. Such signals may be common in apparently cryptic species, and this study once again demonstrates the importance of analysing visual signals beyond the capacity of human vision.

You Are What You Eat: Food Limitation Affects Reproductive Fitness in a Sexually Cannibalistic Praying Mantid

Resource limitation during the juvenile stages frequently results in developmental delays and reduced size at maturity, and dietary restriction during adulthood can affect longevity and reproductive output. Variation in food intake can also result in alteration to the normal pattern of resource allocation among body parts or life-history stages. My primary aim in this study was to determine how varying juvenile and/or adult feeding regimes affect particular female and male traits in the sexually cannibalistic praying mantid Pseudomantis albofimbriata. Praying mantids are sit-and-wait predators whose resource intake can vary dramatically depending on environmental conditions within and across seasons, making them useful for studying the effects of feeding regime on various facets of reproductive fitness. In this study, there was a significant trend/difference in development and morphology for males and females as a result of juvenile feeding treatment, however, its effect on the fitness components measured for males was much greater than on those measured for females. Food-limited males were less likely to find a female during field enclosure experiments and smaller males were slower at finding a female in field-based experiments, providing some of the first empirical evidence of a large male size advantage for scrambling males. Only adult food limitation affected female fecundity, and the ability of a female to chemically attract males was also most notably affected by adult feeding regime (although juvenile food limitation did play a role). Furthermore, the significant difference/trend in all male traits and the lack of difference in male trait ratios between treatments suggests a proportional distribution of resources and, therefore, no trait conservation by food-limited males. This study provides evidence that males and females are under different selective pressures with respect to resource acquisition and is also one of very few to show an effect of juvenile food quantity on adult reproductive fitness in a hemimetabolous insect.

Sexual deception in a cannibalistic mating system? Testing the Femme Fatale hypothesis

Animal communication theory holds that in order to be evolutionarily stable, signals must be honest on average, but significant dishonesty (i.e. deception) by a subset of the population may also evolve. A typical praying mantid mating system involves active mate searching by males, which is guided by airborne sex pheromones in most species for which mate-searching cues have been studied. The Femme Fatale hypothesis suggests that female mantids may be selected to exploit conspecific males as prey if they benefit nutritionally from cannibalism. Such a benefit exists in the false garden mantid Pseudomantis albofimbriata—females use the resources gained from male consumption to significantly increase their body condition and reproductive output. This study aimed to examine the potential for chemical deception among the subset of females most likely to benefit from cannibalism (poorly fed females). Females were placed into one of four feeding treatments (‘Very Poor’, ‘Poor’, ‘Medium’ and ‘Good’), and males were given the opportunity to choose between visually obscured females in each of the treatments. Female body condition and fecundity varied linearly with food quantity; however, female attractiveness did not. That is, Very Poor females attracted significantly more males than any of the other female treatments, even though these females were in significantly poorer condition, less fecund (in this study) and more likely to cannibalise (in a previous study). In addition, there was a positive correlation between fecundity and attractiveness if Very Poor females were removed from the analysis, suggesting an inherently honest signalling system with a subset of dishonest individuals. This is the first empirical study to provide evidence of sexual deception via chemical cues, and the first to provide support for the Femme Fatale hypothesis.