School of BioSciences - Research Publications
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ItemClimate contributes to the evolution of pesticide resistance(WILEY, 2018-02)Abstract Aim The evolution of pesticide resistance through space and time is of great economic significance to modern agricultural production systems, and consequently, is often well documented. It can thus be used to dissect the evolutionary and ecological processes that underpin large‐scale evolutionary responses. There are now nearly 600 documented cases of pesticide resistance in arthropod pests. Although the evolution of resistance is often attributed to the persistent use of chemicals for pest suppression, the rate of development of resistance should also depend on other factors, including climatic conditions that influence population size and generation time. Here, we test whether climatic variables are linked to evolution of resistance by examining the spatial pattern of pyrethroid resistance in an important agricultural pest. Location Southern, agricultural regions of Australia. Time period 2007–2015. Major taxa studied The redlegged earth mite, Halotydeus destructor. Methods We quantified patterns of chemical usage based on paddock histories and collated long‐term climatic data. These data were then compared against presence–absence data on resistance using a boosted regression‐tree approach, applied here for the first time to the spatial categorization of pesticide resistance. Results Although chemical usage was a key driver of resistance, our analysis revealed climate‐based signals in the spatial distribution of resistance, linked to regional variation in aridity, temperature seasonality and precipitation patterns. Climatic regions supporting increased voltinism were positively correlated with resistance, in line with expectations that increased voltinism should accelerate evolutionary responses to selection pressures. Main conclusions Our findings suggest that the prediction of rapid evolutionary processes at continental scales, such as pesticide resistance, will be improved through methods that incorporate climate and ecology, in addition to more immediate selection pressures, such as chemical usage. Boosted regression trees present a powerful tool in the management of resistance issues that has hitherto not been used.
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ItemThe mitogenome of Halotydeus destructor (Tucker) and its relationships with other trombidiform mites as inferred from nucleotide sequences and gene arrangements(WILEY, 2021-10)The redlegged earth mite, Halotydeus destructor (Tucker, 1925: Trombidiformes, Eupodoidea, Penthaleidae), is an invasive mite species. In Australia, this mite has become a pest of winter pastures and grain crops. We report the complete mitogenome for H. destructor, the first to represent the family Penthaleidae, superfamily Eupodoidea. The mitogenome of H. destructor is 14,691 bp in size, and has a GC content of 27.87%, 13 protein-coding genes, two rRNA genes, and 22 tRNA genes. We explored evolutionary relationships of H. destructor with other members of the Trombidiformes using phylogenetic analyses of nucleotide sequences and the order of protein-coding and rRNA genes. We found strong, consistent support for the superfamily Tydeoidea being the sister taxon to the superfamily Eupodoidea based on nucleotide sequences and gene arrangements. Moreover, the gene arrangements of Eupodoidea and Tydeoidea are not only identical to each other but also identical to that of the hypothesized arthropod ancestor, showing a high level of conservatism in the mitogenomic structure of these mite superfamilies. Our study illustrates the utility of gene arrangements for providing complementary information to nucleotide sequences with respect to inferring the evolutionary relationships of species within the order Trombidiformes. The mitogenome of H. destructor provides a valuable resource for further population genetic studies of this important agricultural pest. Given the co-occurrence of closely related, morphologically similar Penthaleidae mites with H. destructor in the field, a complete mitogenome provides new opportunities to develop metabarcoding tools to study mite diversity in agro-ecosystems. Moreover, the H. destructor mitogenome fills an important taxonomic gap that will facilitate further study of trombidiform mite evolution.
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ItemHigh Incidence of Related Wolbachia across Unrelated Leaf-Mining Diptera(MDPI, 2021-09)The maternally inherited endosymbiont, Wolbachia pipientis, plays an important role in the ecology and evolution of many of its hosts by affecting host reproduction and fitness. Here, we investigated 13 dipteran leaf-mining species to characterize Wolbachia infections and the potential for this endosymbiont in biocontrol. Wolbachia infections were present in 12 species, including 10 species where the Wolbachia infection was at or near fixation. A comparison of Wolbachia relatedness based on the wsp/MLST gene set showed that unrelated leaf-mining species often shared similar Wolbachia, suggesting common horizontal transfer. We established a colony of Liriomyza brassicae and found adult Wolbachia density was stable; although Wolbachia density differed between the sexes, with females having a 20-fold higher density than males. Wolbachia density increased during L. brassicae development, with higher densities in pupae than larvae. We removed Wolbachia using tetracycline and performed reciprocal crosses between Wolbachia-infected and uninfected individuals. Cured females crossed with infected males failed to produce offspring, indicating that Wolbachia induced complete cytoplasmic incompatibility in L. brassicae. The results highlight the potential of Wolbachia to suppress Liriomyza pests based on approaches such as the incompatible insect technique, where infected males are released into populations lacking Wolbachia or with a different incompatible infection.
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ItemIdentifying critical research gaps that limit control options for invertebrate pests in Australian grain production systems(WILEY, 2019-02)Abstract Integrated Pest Management (IPM) is often described as a knowledge‐intensive approach to invertebrate pest management, requiring information on the biology, ecology and phenology of a pest combined with an understanding of the interactions between crop growth and pests and between pests and their natural enemies. We conducted a systematic quantitative literature review to summarise what is known about pest and natural enemy species common to Australian grain production systems, based on 1513 published and unpublished research studies. Drawing on this information, we address three issues: what are the knowledge gaps in relation to grain pests and their natural enemies, do these knowledge gaps limit the development of an IPM package for grain growers in Australia and what further ecological or biological information might growers require to enhance the use of IPM approaches for managing pests? The main gaps identified include a lack of understanding around specific factors that lead to pest outbreaks or factors that could be useful for predicting when and where pest outbreaks will occur in the future. Monitoring techniques for many pests are not well developed, and therefore, it is difficult to link the density recorded in a field with crop damage and yield loss and to develop economic thresholds that can be linked with intervention decisions. For most natural enemies, the impact in terms of reduction in pest numbers has not been quantified, with very few studies including both pests and natural enemies together. There is large variability in the level of control provided by natural enemies between years and regions, and the factors leading to this variability are not well understood. Finally, the lack of taxonomic resolution for individual species within groups is identified as a critical knowledge gap. We suggest that a more comprehensive fundamental knowledge base is required across the invertebrate community in grain systems aimed at reducing insect pest outbreaks, combined with a greater depth of understanding in monitoring strategies for pests that contribute to pesticide‐use decisions.
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ItemEscalating insecticide resistance in Australian grain pests: contributing factors, industry trends and management opportunities(JOHN WILEY & SONS LTD, 2019-06)
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ItemClimate, human influence and the distribution limits of the invasive European earwig, Forficula auricularia, in Australia(JOHN WILEY & SONS LTD, 2019-01)
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ItemEmpowering Australian insecticide resistance research with genetic information: the road ahead(WILEY, 2021-02)Abstract Insecticides are important for chemical control of arthropod pests in agricultural systems but select for resistance as an adaptive trait. Identifying the genetic mechanism(s) underpinning resistance can facilitate development of genetic markers, which can be used in monitoring programs. Moreover, understanding of genetic mechanisms in a broader population genetic context can be used to infer the origins of resistance, predict the dynamics of resistance evolution and evaluate the efficacy of different management strategies. Transitioning genetic information successfully into practical solutions requires overcoming two major hurdles. Firstly, genetic mechanisms must be identified to develop genetic markers. Secondly, routine use of genetic markers is required to build substantial spatio‐temporal data on the distribution and frequency of resistance alleles. In this study, we demonstrate large knowledge gaps on the genetic mechanisms of insecticide resistances in Australia using eight established arthropod pests important to the grains industry: Bemisia tabaci (silverleaf whitefly), Frankliniella occidentalis (western flower thrips), Halotydeus destructor (redlegged earth mite), Helicoverpa armigera (cotton bollworm), Myzus persicae (green peach aphid), Plutella xylostella (diamondback moth), Tetranychus urticae (two‐spotted spider mite) and Thrips tabaci (onion thrips). Many resistances have not been characterised at the genetic level in most pests, even for chemical MoA groups with a long history of use in Australia. Moreover, monitoring of resistance is spatio‐temporally patchy, which precludes examination of long‐term trends or predictive modelling. We suggest that leveraging cumulative global knowledge of resistances to develop a priori candidate genes, and incorporation of genomic approaches, can help overcome the hurdles of embracing genetic information in resistance management. We highlight the recently invasive Spodoptera frugiperda (fall armyworm) as a case study where genetic markers and genomic approaches should prove useful in rapidly assessing the risk of this species to the Australian grains industry and other agricultural commodities. The uptake of genetic information into management can only occur once its benefit to empower insecticide resistance research is fully realised. Ultimately, the road ahead requires amalgamation of multifaceted data (genes, environment and spatio‐temporal replication) to better understand and predict the dynamics of resistance evolution.
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ItemPotential for biological control of the vegetable leafminer, Liriomyza sativae (Diptera: Agromyzidae), in Australia with parasitoid wasps(WILEY, 2020-02)Abstract The vegetable leafminer, Liriomyza sativae Blanchard, poses a risk to vegetable and nursery production in mainland Australia since established in Cape York in 2015. Effective control overseas depends on maximising the impact of natural enemies. Problems with polyphagous Liriomyza pest species typically result from the destruction of their parasitoids by excessive use of non‐selective insecticides. Field studies are reviewed to identify parasitoid species involved in the biological control of L. sativae in open‐air and glasshouse production internationally and to assess the current knowledge of parasitoids of agromyzids in Australia. Overseas, invading Liriomyza populations have frequently been exploited by endemic parasitoids (often found on non‐pest agromyzid species), and non‐crop hosts have played a role as reservoirs of these parasitoids. The few published Australian field studies on the occurrence of agromyzid flies and their parasitoids show a large community of wasps attacking agromyzids, with species mainly from the Eulophidae, Pteromalidae and Braconidae. The most abundant recorded species are two cosmopolitan eulophid species, Hemiptarsenus varicornis (Girault) and Diglyphus isaea (Walker), and four Australian species: two eulophid species, Zagrammosoma latilineatum Ubaidillah and Closterocerus mirabilis Edwards & La Salle, one pteromalid species, Trigonogastrella sp., and one braconid species, Opius cinerariae Fischer, for which there is little biological information. One deficiency in the known assemblage in Australia is the absence of parasitoids from the Eucoilinae (Hymenoptera: Figitidae), a subfamily with several abundant species attacking agromyzids overseas. The composition and impact of the endemic parasitoid assemblage in Australia on populations of L. sativae needs to be assessed adequately in the field before the importation of additional exotic parasitoid species is contemplated. Overseas, two species, D. isaea and Dacnusa sibirica Telenga, are reared commercially for augmentative biological control, although the relatively high cost of production has restricted their release to protected cropping situations. Knowledge gaps remain locally about the taxonomy, distribution, host range and life cycle of parasitoids, and their potential impact on L. sativae.