Katherine (Kate) L Barry

Abstract: Many sensory modes can be exploited to determine the location of potential mates. In insects, long-distance location primarily involves chemical or acoustic cues, whereas short-distance communication mainly utilises visual or tactile cues. The structural complexity of the environment may influence the transmission of information, and therefore, it is common to see multiple sensory modes employed to increase the likelihood of accurate mate location. Praying mantids are known to use airborne chemicals for long-distance location and visual cues in close proximity. This study examined which types of cues are used for mate location in an unstudied species, Hierodula majuscula, from Queensland, Australia. The timing of female pheromone emission during �calling� periods reached a peak at 3:00 h, with the majority of females assuming a calling posture at this time. Scanning electron microscopy was used to confirm the presence of basiconic sensilla (used for chemical reception) on male antennae, and males successfully responded to female chemical cues and subsequently located potential mates. Males were not as successful at finding females when restricted to using visual cues.

Abstract: 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.

Abstract: Sperm competition occurs when a female mates with more than one male, and the sperm of those males compete directly over fertilizing her eggs. In polyandrous animals, males can respond to the perceived risk of sperm competition by flexibly adjusting aspects of their development and reproductive investment. In high-risk scenarios we might expect males to accelerate development so as to mature quickly and locate receptive females first and/or transfer more sperm so as to outcompete rival sperm. We examined these predictions using the false garden mantid, Pseudomantis albofimbriata, a medium-sized praying mantid found on the east coast of Australia. Males are less than half the mass of females. Sexual cannibalism occurs in up to 40% of interactions, highlighting the importance of investing optimally in reproductive opportunities for males. We housed juvenile males in two operational sex ratio treatments: three males, one female (high risk of sperm competition) and one male, three females (low risk). We found no evidence of accelerated development in the high-risk group; instead, high-risk males took longer to mature. Possibly, males exposed to a higher risk of sperm competition delay maturity in order to invest in testes development and sperm production. We also found that males reared in the high-risk treatment transferred significantly more sperm than males reared in the low-risk treatment, providing evidence of strategic ejaculation in male P. albofimbriata. This is the first study demonstrating a male response to the perceived risk of sperm competition via delayed development and increased ejaculate investment in praying mantids.

Abstract: 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 cannibalise 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 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.

Abstract: 1. Female feeding regime exhibited a cascade of effects on reproductive biology and behaviour in the mantid Stagmomantis limbata (Hahn). 2. Well-fed females (High diet) consistently attained greater body mass, thicker abdomens, and higher fecundity than food-limited females (Low diet) in four annual generations. Dorso-ventral abdominal thickness strongly correlated with fecundity. 3. In an experiment in captivity, Low diet females were more likely to cannibalize males than High diet females. 4. High diet females attracted more males than Low diet females in several contexts. In terms of long-range attraction, caged High diet females attracted more males in the field. In terms of short-range attraction, males preferentially mounted and copulated with High diet females in captive paired choice trials. In naturally-occurring pairs in the field, a preference for females with thick abdomens was evident. These results point to two possible explanations: male choice for well-fed females and state dependent female pheromone emission. 5. Two years of field data indicate considerable variation in female feeding success, as measured by abdominal thickness. Average feeding success in nature appears to be relatively high, when comparing the rate of abdominal expansion in the field to captive females maintained on High diets. 6. In the field, nearly all mounts and copulations occurred in September in both years, when female feeding success is expected to be high. If mating activity occurs during a window of high female feeding success, so as to reduce the risk of cannibalism for males, then female feeding regime may be implicated in the phenology of mating activity in cannibalistic species.

Abstract: 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 who 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 mate choice is better phrased as a question of �why 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.

Abstract: The traditional view of sexual selection has been that of competing males and choosy females, however, more recently it has been recognized that males may exhibit mate choice when females vary in quality and when males suffer costs associated with mating. Sexually cannibalistic mating systems provide an opportunity to examine male mate choice further: the high costs potentially involved in the mating process for males, as well as variation in female quality, predicts male mate choice. Here, we use the praying mantid Pseudomantis albofimbriata to determine the effect of female body condition on male mate choice in a system with frequent pre-copulatory sexual cannibalism. Female body condition is positively correlated with fecundity and negatively correlated with the propensity to cannibalise, so we predict males will exhibit strong male mate choice for good-condition females to maximize their reproductive potential. Results of our simultaneous choice tests showed that males use chemical and visual cues for mate location and assessment, and that they can use either of these sensory modalities to distinguish and choose between females of varying body condition, with a significant 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 us that even when female quality varies and the cost of mating for males is substantial, male mate rejection does not always evolve.

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, while 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, while visual cues and signals become important at shorter range.

Abstract: 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.

Abstract: Several hypotheses have been proposed to explain the evolution of sexual cannibalism. The foraging strategy hypothesis states that sexual cannibalism may arise as an adaptive foraging strategy, providing females with the nutrients to increase future fecundity. Yet, very few studies have found that nourishment through cannibalism translates into increased fecundity. One explanation for this may be that most of these investigations have concentrated on sexually dimorphic spider species with tiny males that do not significantly increase female body mass on consumption. The current study focuses on the praying mantid, Pseudomantis albofimbriata, a moderately size dimorphic species with relatively large males. Cannibalistic females of such species may be more likely to gain nutritional benefits from male consumption, which translate into increased fecundity. Here, cannibalistic females substantially improved their body condition and subsequently produced heavier egg cases than their noncannibalistic counterparts. An additional prediction of the foraging strategy hypothesis is that sexual cannibalism will increase with decreasing female condition. We found that the prevalence of sexual cannibalism in this system was indeed affected by female body condition; females in poor condition were more likely to consume their potential mates than females in good condition. Additional analysis of the data refuted the relevance of each of the remaining hypotheses for this species, providing clear evidence for the foraging strategy hypothesis as an explanation for the maintenance of sexual cannibalism in this species.

Abstract: The sensory systems employed by animals to locate potential mates are diverse. Among insects, chemical and acoustic signals are commonly used over long distances, with visual signals playing a role in close-range orientation and courtship. Within groups that exhibit a scramble competition mating system, selection on mate searching ability will be particularly strong. Clearly, aspects of the species ecology, such as habitat complexity and population density, will be crucial in the evolution of mate searching systems and sexual signals. Praying mantids exhibit both chemical and visual sexual signalling behaviour, and also vary in their ecology. This study employs scanning electron microscopy of antennal sensory morphology and behavioural assays to investigate the relative importance of chemical and visual signalling in two Australian praying mantid species: Pseudomantis albofimbriata and Ciulfina biseriata . As predicted, the high level of habitat complexity, low population density and strong male dispersal capability of P. albofimbriata corresponded to the use of airborne sex pheromones. Conversely, the open habitat, high population density, and poor dispersal of C. biseriata corresponded to a greater reliance on short-range visual cues for mate location.

Abstract: Most birds rely on imprinting and experience with conspecifics to learn species-specific recognition cues. Australian brush-turkeys (Alectura lathami) do not imprint and form no bonds with parents. They hatch asynchronously, disperse widely and meet juvenile conspecifics at an unpredictable age. Nevertheless, in captivity, hatchlings respond to other chicks. A recent study, which involved the use of robotic models, found that chicks prefer to approach robots that emit specific visual cues. Here, we evaluated their response to acoustic cues, which usually play an important role in avian social cognition. However, in simultaneous choice tests, neither 2-day-old nor 9-day-old chicks preferred the choice arm with playback of either chick or adult conspecific calls over the arm containing a silent loudspeaker. Chicks of both age classes, however, scanned their surroundings more during chick playback, and the response was thus consistent in younger and older chicks. We also presented the chicks with robotic models, either with or without playback of chick calls. They did not approach the calling robot more than they did the silent robot, indicating that the combination of visual and acoustic cues does not evoke a stronger response. These results will allow further comparison with species that face similar cognitive demands in the wild, such as brood parasites. Such a comparative approach, which is the focus of cognitive ecology, will enable us to further analyse the evolution and adaptive value of species recognition abilities.

Abstract: In the field, only around 60% of male St Andrew's Cross spiders survive their first mating, with many of the surviving individuals losing their legs while attempting to escape from a female. Surprisingly, 67% of males that survive by leaping off the female's web return almost immediately to her web where they remain for several hours. However, males did not remate with the female. Laboratory experiments revealed that males remaining on the web can prevent females from remating with rival males entering the web. In the absence of a male, 75% of females remated with a second male, while only 47% of the females were able to remate with the second male if the first male was present. The guarding male engages rivals in physical contests, and even if the female remates, the presence of the guarding male reduces the duration of copulation.