Browsing by Author "Judge, Kevin"

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    An abdominal stridulation organ in Cyphoderris (Prophalangopsidae) and concerning the systematic classification of the Ensifera (Saltatoria)
    (2021-01-11) Ander, Kjell; Sander, Barbara; Judge, Kevin; translated.com
    Ensiferan insects (crickets, katydids, grigs and allies) are well known for rubbing parts of their cuticle together to produce sound: a process called stridulation. In this article Swedish entomologist Kjell Ander describes a novel (at the time) stridulatory apparatus in the great grig, Cyphoderris monstrosa (Prophalangopsidae), a relict ensiferan found in the mountainous regions of western North America. Ander used preserved specimens to predict the sound-producing function of a pair of abdominal file-scraper apparatuses, although he was never able to directly test his proposed mechanism nor did he speculate as to the adaptive significance of the structures. The article concludes with a review of the systematic placement of various higher level taxa within the order Orthoptera, of which Ensifera is one suborder.
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    Behavioural and mechanical isolation in the Great Grig, Cyphoderris monstrosa
    (2020) Dennis, Miranda; Judge, Kevin
    The Great Grig (Cyphoderris monstrosa) is a species that has shown evidence of possibly being in the early stages of speciation. This study uses mating trials to determine the degree of isolation between the Alberta and British Columbia populations behaviourally and looking at the morphology of the populations to determine the possibility of mechanical isolation in C. monstrosa, possibly representing pre-zygotic mating barriers. If C. monstrosa is in the early stages of speciation, then it is predicted that there will be distinct differences between the grigs, specifically behavioural differences seen when attempting to mate the two groups, and morphological differences in their genitalia. Analyses of behaviour and morphology showed that the two populations were significantly different in aspects of size and form of genitalia, with the Alberta grigs being larger than the British Columbia grigs. This finding is concurrent with other studies, indicating the possibility of speciation between the populations, as per the biological species concept. This study helps to answer questions regarding species concepts and speciation in the Great Grig, as well as indicates the need for future work with these insects.
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    Body size and lifespan are condition dependent in the mealworm beetle, Tenebrio molitor, but not sexually-selected traits
    (2018) McConnell, Murray; Judge, Kevin
    Traits under strong directional selection are predicted to be condition dependent, and thus increase in development when an organism acquires more resources. This prediction has been tested for a variety of traits, particularly those under precopulatory sexual selection. However, few studies compare the condition dependence of a variety of phenotypic traits, potentially subject to different selective forces. Here we examine the condition dependence of several important life history traits, including those under both pre- and postcopulatory sexual selection, in the mealworm beetle, Tenebrio molitor. We manipulated condition by randomly assigning larvae to one of: high-, medium- or low-quality diets. For males reared on the three diets we measured: a) adult body size and lifespan, b) pheromone attractiveness, c) weight of their ejaculate transferred to females, and d) fecundity of their female mates. Males raised on a high-diet were larger and lived longer than males raised on medium- and low-diets. Although females were significantly attracted to male pheromones, there were no significant differences amongst condition treatments in male attractiveness, nor ejaculate transfer. Furthermore, mates’ fecundity was also not affected by male condition. We discuss these results considering previous work on trade-offs and condition dependence of life history traits.
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    Condition dependence of male lifespan and calling effort in a field cricket
    (2008) Judge, Kevin; Ting, Janice J.; Gwynne, Darryl T.
    Sexually selected traits are thought to impose survival costs on showy males. Recent empirical work found a negative relationship between male display and survival in a field cricket species (Orthoptera, Gryllidae, Gryllinae) where there is no evidence of a mating bias towards older males. In most species, however, male survival and ornamentation are positively correlated, and older males often have a mating success advantage over younger males. These findings suggest that male quality and survival are positively correlated, but more tests of this hypothesis are needed. We measured the condition dependence of male survival and mating investment (calling effort) in another grylline, Gryllus pennsylvanicus, where older males have previously been shown to have greater mating success. We varied condition by manipulating diet, and measured male lifespan and calling effort to assess the relative condition dependence of these traits. High and medium condition males survived longer than low condition males, and high condition males called more than medium and low condition males. Differences in calling effort among the condition treatments were not apparent early in life, but emerged as males aged. We discuss possible explanations for the differences between our study and contrasting results such as the previous grylline work.
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    Does hunger lead to hybridization in a genus of sexually cannibalistic insects (Orthoptera: Prophalangopsidae)?
    (2020) Dupuis, Julian R.; Judge, Kevin; Brunet, Bryan M. T.; Ohlmann Chan, Shawna; Sperling, Felix A. H.
    Allochronic isolation can be a strong mechanism for reproductive isolation and speciation. However, imperfect allochrony and the expression of phenological plasticity can erode temporal barriers to gene flow and result in hybridization between divergent lineages. Here, we combine behavioural ecology and genomics to investigate this scenario in two closely related species of grigs in the genus Cyphoderris. These species exhibit a unique mating system whereby females feed on the fleshy hind wings of the male during copulation, and copulation with conspecific males is more likely in food-restricted females than in well-fed females. In western Canada, Cyphoderris buckelli and Cyphoderris monstrosa are sympatric but largely allochronically separated, with C. buckelli breeding earlier. However, their breeding seasons can overlap, leading to potential for older C. buckelli females to mate with young C. monstrosa males to obtain resources via sexual cannibalism. We used behavioural assays to test whether female feeding status affects the propensity for interspecific mating between C. buckelli females and C. monstrosa males. We then tested for hybridization and gene exchange in wild populations of both species, using morphology, mitochondrial DNA and genome-wide nuclear markers. We found that interspecific courtship and mating can occur, but the relationship between food restriction and increased propensity for hybridization was not significant. Although we observed intraspecific population genetic structure in both species, we found no signatures of hybridization in the morphological or genetic datasets, which suggests that postmating reproductive barriers might be preventing successful hybridization in the wild.
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    Elucidating the distribution of a non-native katydid in Alberta using bioacoustics
    (2020) Caouette, Alexandre; Judge, Kevin
    Accumulating evidence has shown that climate change is causing shifts in species distributions. Several Orthoptera (grasshoppers, crickets, and katydids) species have been shifting their ranges in response to rising annual temperatures. Bioacoustics is a useful tool for monitoring this shift in populations distributions because Orthoptera produce audible vocalizations and can be captured by recording devices. Recently, Roeseliana roeselii, a species of Orthoptera native to Europe, was discovered near Edmonton, Alberta, outside of its naturalized range in eastern North America. This discovery presents a unique opportunity to elucidate the provincial distribution of R. roeselii by using bioacoustics software. In this project, I used automated audio recognition software to sort through province-wide field recordings from the Alberta Biodiversity Monitoring Institute (ABMI) to evaluate the feasibility of using bioacoustics for R. roeselii in Alberta and report any new records or observations. Using field and lab collected recordings of R. roeselii, an algorithm is created to sort through over 10,000 hours of audio. In all these recordings I was unable to detect R. roeselii calls in the ABMI recording data despite finding multiple populations through field sampling. This project lays the groundwork to better understand R. roeselii’s distribution in North America and comments on the possibility for using automated acoustics for other Orthoptera species in North America.
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    Immune response of field crickets (Gryllus firmus) to eugregarine parasites (apicomplexan protoza)
    (2015) Shaw, Ashley; Judge, Kevin; Stock, Michael
    This research concerns the immunity response of the crickets Gryllus firmus. The immunity response is measured by the crickets' encapsulation response, which is a response of the insects blood cells which surround the insect and darken, or become melanized. It is assumed that the higher the melanization, the higher the immune response. The unique feature of these crickets is that they are infected with eugregarine gut parasites, and there has been no previous studies on these parasites within this species of crickets.
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    Listening to male song induces female field crickets to differentially allocate reproductive resources
    (2017) Ting, Janice J.; Judge, Kevin; Gwynne, Darryl T.
    Differential investment in offspring by mothers is predicted when there is substantial variation in sire quality. Whether females invest more resources in the offspring of high-quality mates (differential allocation, DA) or in the offspring of low-quality mates (reproductive compensation, RC) is not consistent in the literature and both effects can be predicted by theoretical models. In the field cricket, Gryllus pennsylvanicus Burmeister, 1838 (Orthoptera: Gryllidae: Gryllinae), females are attracted more to calling songs of high-quality males than to those of low-quality males. We tested whether females invest reproductive resources differentially based on perceived mate quality. We manipulated female perception of male quality by allowing virgin females to approach a speaker broadcasting either high- or low-quality calling song (high or low calling effort respectively), and then mated them with a randomly chosen male that had been rendered incapable of calling. In the week following mating, females exposed to high-quality calling song gained less weight, laid more embryos, and laid larger embryos than females exposed to low-quality calling song, although only the first of these effects was statistically significant. These results support the DA hypothesis and suggest that females invest their reproductive output based on a trait (calling effort) that is an honest indicator of male quality.
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    Male weaponry in a fighting cricket
    (2008) Judge, Kevin; Bonanno, Vanessa
    Sexually selected male weaponry is widespread in nature. Despite being model systems for the study of male aggression in Western science and for cricket fights in Chinese culture, field crickets (Orthoptera, Gryllidae, Gryllinae) are not known to possess sexually dimorphic weaponry. In a wild population of the fall field cricket, Gryllus pennsylvanicus, we report sexual dimorphism in head size as well as the size of mouthparts, both of which are used when aggressive contests between males escalate to physical combat. Male G. pennsylvanicus have larger heads, maxillae and mandibles than females when controlling for pronotum length. We conducted two experiments to test the hypothesis that relatively larger weaponry conveys an advantage to males in aggressive contests. Pairs of males were selected for differences in head size and consequently were different in the size of maxillae and mandibles. In the first experiment, males were closely matched for body size (pronotum length), and in the second, they were matched for body mass. Males with proportionately larger weaponry won more fights and increasing differences in weaponry size between males increased the fighting success of the male with the larger weaponry. This was particularly true when contests escalated to grappling, the most intense level of aggression. However, neither contest duration nor intensity was related to weaponry size as predicted by models of contest settlement. These results are the first evidence that the size of the head capsule and mouthparts are under positive selection via male-male competition in field crickets, and validate 800-year-old Chinese traditional knowledge.
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    Multivariate sexual selection on male song structure in wild populations of sagebrush crickets, Cyphoderris strepitans (Orthoptera: haglidae)
    (2013) Ower, Geoffrey D.; Judge, Kevin; Steiger, Sandra; Caron, Kyle J.; Smith, Rebecca A.; Hunt, John; Sakaluk, Scott K.
    While a number of studies have measured multivariate sexual selection acting on sexual signals in wild populations, few have confirmed these findings with experimental manipulation. Sagebrush crickets are ideally suited to such investigations because mating imposes an unambiguous phenotypic marker on males arising from nuptial feeding by females. We quantified sexual selection operating on male song by recording songs of virgin and mated males captured from three wild populations. To determine the extent to which selection on male song is influenced by female preference, we conducted a companion study in which we synthesized male songs and broadcast them to females in choice trials. Multivariate selection analysis revealed a saddle-shaped fitness surface, the highest peak of which corresponded to longer train and pulse durations, and longer intertrain intervals. Longer trains and pulses likely promote greater mate attraction, but selection for longer intertrain durations suggests that energetic constraints may necessitate “time outs”. Playback trials confirmed the selection for longer train and pulse durations, and revealed significant stabilizing selection on dominant frequency, suggesting that the female auditory system is tightly tuned to the species-specific call frequency. Collectively, our results revealed a complex pattern of multivariate nonlinear selection characterized primarily by strong stabilizing and disruptive selection on male song traits.
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    The Ander's organ: a mechanism for anti-predator ultrasound in a relict orthopteran
    (2021) Woodrow, C.; Judge, Kevin; Pulver, C.; Jonsson, T.; Montealegre-Z, F.
    The use of acoustics in predator evasion is a widely reported phenomenon amongst invertebrate taxa, but the study of ultrasonic anti-predator acoustics is often limited to the prey of bats. Here, we describe the acoustic function and morphology of a unique stridulatory structure – the Ander's organ – in the relict orthopteran Cyphoderris monstrosa (Ensifera, Hagloidea). This species is one of just eight remaining members of the family Prophalangopsidae, a group with a fossil record of over 90 extinct species widespread during the Jurassic period. We reveal that the sound produced by this organ has the characteristics of a broadband ultrasonic anti-predator defence, with a peak frequency of 58±15.5 kHz and a bandwidth of 50 kHz (at 10 dB below peak). Evidence from sexual dimorphism, knowledge on hearing capabilities and assessment of local predators, suggests that the signal likely targets ground-dwelling predators. Additionally, we reveal a previously undescribed series of cavities underneath the organ that probably function as a mechanism for ultrasound amplification. Morphological structures homologous in both appearance and anatomical location to the Ander's organ are observed to varying degrees in 4 of the 7 other extant members of this family, with the remaining 3 yet to be assessed. Therefore, we suggest that such structures may either be more widely present in this ancient family than previously assumed, or have evolved to serve a key function in the long-term survival of these few species, allowing them to outlive their extinct counterparts.
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    The identity of the Bahama endemic field cricket Gryllus bryanti Morse (Orthoptera: Gryllidae; Gryllinae; Gryllini)
    (2019) Weissman, David B.; de Luca, Paul Anthony; Judge, Kevin; Gray, David A.
    The Bahama endemic field cricket, Gryllus bryanti Morse, 1905, previously known from only the lost female holotype, is redescribed, including designation of a neotype. Known only from Andros and Eleuthera Islands in The Bahamas, where it occurs with G. assimilis, it can be separated from the latter by song, tegmen file characteristics, head wider than pronotum, and genetics.