School of BioSciences - Research Publications
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ItemGenome-wide SNPs of vegetable leafminer, Liriomyza sativae: Insights into the recent Australian invasion(WILEY, 2022-07)Liriomyza sativae, the vegetable leafminer, is an important agricultural pest originally from the Americas, which has now colonized all continents except Antarctica. In 2015, L. sativae arrived on the Australian mainland and established on the Cape York Peninsula in the northeast of the country near the Torres Strait, which provides a possible pathway for pests to enter Australia and evade biosecurity efforts. Here, we assessed genetic variation in L. sativae based on genome-wide single nucleotide polymorphisms (SNPs) generated by double digest restriction-site-associated DNA sequencing (ddRAD-seq), aiming to uncover the potential origin(s) of this pest in Australia and contribute to reconstructing its global invasion history. Our fineRADstructure results and principal component analysis suggest Australian mainland populations were genetically close to populations from the Torres Strait, whereas populations from Asia, Africa, and Papua New Guinea (PNG) were more distantly related. Hawaiian populations were genetically distinct from all other populations of L. sativae included in our study. Admixture analyses further revealed that L. sativae from the Torres Strait may have genetic variation originating from multiple sources including Indonesia and PNG, and which has now spread to the Australian mainland. The L. sativae lineages from Asia and Africa appear closely related. Isolation-by-distance (IBD) was found at a broad global scale, but not within small regions, suggesting that human-mediated factors likely contribute to the local spread of this pest. Overall, our findings suggest that an exotic Liriomyza pest invaded Australia through the Indo-Papuan conduit, highlighting the importance of biosecurity programs aimed at restricting the movement of pests and diseases through this corridor.
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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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ItemBiology, ecology and management of Diuraphis noxia (Hemiptera: Aphididae) in Australia(WILEY, 2020-05)Abstract The Russian wheat aphid, Diuraphis noxia (Mordvilko ex Kurdjumov), is one of the world's most economically important pests of grain crops and has been recorded from at least 140 grass species within Poaceae. It has rapidly dispersed from its native origin of Central Asia into most major grain‐producing regions of the world including Africa, Asia, Europe, the Middle East, North America and South America. Diuraphis noxia was first found in Australia in a wheat crop in the mid‐north of South Australia in May 2016. Since then, D. noxia has been recorded throughout grain‐growing regions of South Australia, Victoria, New South Wales and Tasmania. The distribution will continue to expand, with climatic suitability modelling suggesting D. noxia can persist in all key grain regions, including large parts of Western Australia and Queensland. Australian populations of D. noxia appear to be anholocyclic, with no sexual stages being observed. The aphids can reproduce year round as long as host plants are available. Australian farmers have generally adopted prophylactic insecticide seed treatments and/or foliar sprays to manage D. noxia. Research is required to fully understand yield impacts, host preferences and host plant resistance associated with D. noxia. Cultural control through managing alternate host plants over summer, agronomic crop management, biological control and developments in host plant resistance should provide considerable future benefits.
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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.
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ItemVariation in sex ratio of the leafminer Phytomyza plantaginis Goureau (Diptera: Agromyzidae) from Australia(WILEY, 2021-08)Abstract Parthenogenetic reproduction has only previously been demonstrated in two species of agromyzid leafminer flies (Diptera: Agromyzidae), both from the genusPhytomyza. The plantain leafminer,Phytomyza plantaginis, is Palaearctic in origin, and bisexual populations have been observed in this region. However, historically, only females had been collected in the Australasian, Nearctic, Neotropical and Oceanian regions. Here, we show that southern Australian samples of this species fromPlantagospp. can be composed of both parthenogenic and bisexual populations. In sites around Melbourne, males were present, although the sex ratio was female biased, with females comprising 75% of sampled individuals. In contrast, males were absent from collections in western and northern Victoria, Australian Capital Territory, New South Wales and Western Australia. FemaleP. plantaginisflies were reared from threePlantagohost plants (Plantago lanceolata,Plantago majorandPlantago coronopus), although females were particularly common fromPl. lanceolata. Insect cages set up with leafminers from sites where only females occurred produced only females, while cages with leafminers from sites where males occurred produced both sexes and mating was observed. Individuals from all populations were infected byWolbachiaendosymbionts, suggesting that the presence/absence ofWolbachiais not directly responsible for the parthenogenesis. However, there was an association between a mtDNA variant (PP.02) and sexual reproduction, in that this variant was absent in areas where only females were collected but present in all males and some females from areas with sexual populations. The mechanism responsible for parthenogenesis inP. plantaginisremains unknown but is linked to maternal factors.