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Johan Liljeblad - One of the best experts on this subject based on the ideXlab platform.
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adding another piece to the cynipoid puzzle the description of a new tribe genus and species of Gall Wasp hymenoptera cynipidae endemic to the republic of south africa
Zootaxa, 2011Co-Authors: Johan Liljeblad, Jose Luis Nievesaldrey, Stefan Neser, George MelikaAbstract:Larvae and adult females of a single species inducing Galls on Scolopia mundii (Salicaceae) are described as Qwaqwaia scolopiae Liljeblad, Nieves-Aldrey & Melika sp. n. The genus Qwaqwaia Liljeblad, Nieves-Aldrey & Melika gen. n. is also described as new and placed in a tribe, Qwaqwaiini Liljeblad, Nieves-Aldrey & Melika trib. n., herein erected to encompass this sole species. Diagnostic characters and a key to all eight cynipid tribes are given. With its unique South African distribution and seemingly plesiomorphic morphology, this Gall Wasp is important for the future untangling of the early evolution of the microcynipoids.
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EVOLUTION OF THE Gall Wasp–HOST PLANT ASSOCIATION
Evolution, 2001Co-Authors: Fredrik Ronquist, Johan LiljebladAbstract:Gall Wasps, or cynipids, form the second largest radiation of Galling insects with more than 1300 described species. According to current views, the first cynipids were phytophagous and developed in herb stems of the Asteraceae without modifying plant growth or development. The first Galls were supposedly multichambered stem swellings, and subsequent trends involved increase in Gall complexity and reduction in the number of larval chambers. Gall Wasps also have many of the features believed to be characteristic for phytophagous insects radiating in parallel with their host plants. We tested these hypotheses by mapping characters onto a recent estimate of higher cynipid relationships from a morphology-based analysis of exemplar taxa, controlling for phylogenetic uncertainty using bootstrapping. Characters were also mapped onto a metatree including all Gall Wasps, assembled from phylogenetic analyses as well as recent classifications. The results contradict many of the current hypotheses. The first cynipids with extant descendants were not Asteraceae stem feeders but induced distinct single-chambered Galls in reproductive organs of herbaceous Papav- eraceae, or possibly Lamiaceae. There has been a general trend toward more complex Galls but the herb-stem feeders evolved from ancestors inducing distinct Galls and their larval chambers are best understood as cryptic Galls. Woody hosts have been colonized only three times, making the apparently irreversible transition from herbs to woody hosts one of the most conservative features of the Gall Wasp-host plant association. The evolution of host plant preferences is characterized by colonization of preexisting host-plant lineages rather than by parallel cladogenesis. Cynipids are mono- or oligophagous and host-plant choice is strongly phylogenetically conserved. Yet, the few major host shifts have involved remarkably distantly related plants. Many shifts have been onto plant species already exploited by other Gall Wasps, suggesting that interspecific parasitism among cynipids facilitates colonization of novel host plants.
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evolution of the Gall Wasp host plant association
Evolution, 2001Co-Authors: Fredrik Ronquist, Johan LiljebladAbstract:Gall Wasps, or cynipids, form the second largest radiation of Galling insects with more than 1300 described species. According to current views, the first cynipids were phytophagous and developed in herb stems of the Asteraceae without modifying plant growth or development. The first Galls were supposedly multichambered stem swellings, and subsequent trends involved increase in Gall complexity and reduction in the number of larval chambers. Gall Wasps also have many of the features believed to be characteristic for phytophagous insects radiating in parallel with their host plants. We tested these hypotheses by mapping characters onto a recent estimate of higher cynipid relationships from a morphology-based analysis of exemplar taxa, controlling for phylogenetic uncertainty using bootstrapping. Characters were also mapped onto a metatree including all Gall Wasps, assembled from phylogenetic analyses as well as recent classifications. The results contradict many of the current hypotheses. The first cynipids with extant descendants were not Asteraceae stem feeders but induced distinct single-chambered Galls in reproductive organs of herbaceous Papav- eraceae, or possibly Lamiaceae. There has been a general trend toward more complex Galls but the herb-stem feeders evolved from ancestors inducing distinct Galls and their larval chambers are best understood as cryptic Galls. Woody hosts have been colonized only three times, making the apparently irreversible transition from herbs to woody hosts one of the most conservative features of the Gall Wasp-host plant association. The evolution of host plant preferences is characterized by colonization of preexisting host-plant lineages rather than by parallel cladogenesis. Cynipids are mono- or oligophagous and host-plant choice is strongly phylogenetically conserved. Yet, the few major host shifts have involved remarkably distantly related plants. Many shifts have been onto plant species already exploited by other Gall Wasps, suggesting that interspecific parasitism among cynipids facilitates colonization of novel host plants.
George Melika - One of the best experts on this subject based on the ideXlab platform.
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Time-since fire and cynipid Gall Wasp assemblages on oaks
Biodiversity and Conservation, 2020Co-Authors: James T. Cronin, George Melika, Warren G AbrahamsonAbstract:Fires are ubiquitous features of many terrestrial ecosystems and can greatly impact the structure and evolution of plant communities. However, much less is known about how fire history impacts higher trophic levels. Using detailed records on the history and intensity of fires at the Archbold Biological Station (ABS) in central Florida, USA, we examined how time-since-fire affects the cynipid Gall Wasp assemblage (Hymenoptera: Cynipidae) associated with four oak species ( Quercus ) that are dominant components of the plant community in this region. Cynipid abundance, richness and diversity were quantified from 1249 oak trees/shrubs in 20 sites that varied in time-since-fire from 1.5 to 91 years. Among all sites and oaks, we found 24 species of cynipids and there was very little species overlap among oak species, even within the same site. Gall abundance increased with time-since-fire and was correlated with tree height, suggesting that available host material or plant architecture may be a primary driver of cynipid recovery. Within 3 years of a fire, 14 of the 23 cynipid species were detected among the sites, and by seven years since fire, all but two species could be detected. Overall, species richness and diversity reached an asymptote within ≈ 7 years. Given how quickly the cynipid assemblage recovers after a fire, frequent fires at ABS are unlikely to negatively impact these insects. However, in smaller or more isolated scrub-oak fragments, recovery could be much slower.
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the asian chestnut Gall Wasp dryocosmus kuriphilus a global invader and a successful case of classical biological control
Journal of Pest Science, 2019Co-Authors: Dimitrios N Avtzis, George Melika, Dinka Matosevic, David R CoyleAbstract:Native to China, the Asian chestnut Gall Wasp, Dryocosmus kuriphilus (ACGW), was first found outside its native range in Japan and the Korean peninsula in the mid-twentieth century. After appearing in North America in 1974, it was found in Europe a few decades later. Since then, the Gall Wasp has spread throughout the distribution of chestnut in Europe. The ACGW’s discovery in North America and Europe elicited numerous studies to understand its invasive potential in these areas and how to control its spread and impact on chestnut production. Although endemic parasitoids responded positively to D. kuriphilus with low parasitism rates, the most effective management tactic has been classical biological control via the introduction of the parasitoid Torymus sinensis from its native range in China. This review summarizes the history of introduction, spread, and current distribution of D. kuriphilus, and highlights one of the most successful cases of classical biological control against a forest pest.
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population dynamics of native parasitoids associated with the asian chestnut Gall Wasp dryocosmus kuriphilus in italy
Psyche: A Journal of Entomology, 2018Co-Authors: Tiziana Panzavolta, George Melika, Francesco Croci, Matteo Bracalini, Stefano Benedettelli, Guido Tellini Florenzano, Riziero TiberiAbstract:Native parasitoids may play an important role in biological control. They may either support or hinder the effectiveness of introduced nonnative parasitoids released for pest control purposes. Results of a three-year survey (2011–2013) of the Asian chestnut Gall Wasp (ACGW) Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) populations and on parasitism rates by native indigenous parasitoids (a complex of chalcidoid hymenopterans) in Italian chestnut forests are given. Changes in D. kuriphilus Gall size and phenology were observed through the three years of study. A total of 13 species of native parasitoids were recorded, accounting for fluctuating parasitism rates. This variability in parasitism rates over the three years was mainly due to the effect of Torymus flavipes (Walker) (Hymenoptera: Torymidae), which in 2011 accounted for 75% of all parasitoid specimens yet decreased drastically in the following years. This strong fluctuation may be related to climatic conditions. Besides, our data verified that parasitoids do not choose host Galls based on their size, though when they do parasitize smaller ones, they exploit them better. Consequently, ACGWs have higher chances of surviving parasitism if they are inside larger Galls.
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tournament abc analysis of the western palaearctic population history of an oak Gall Wasp synergus umbraculus
Molecular Ecology, 2017Co-Authors: Graham N Stone, Karsten Schönrogge, George Melika, Sarah C White, Gyorgy Csoka, Serap Mutun, Zsolt Penzes, Ebrahim S Sadeghi, Majid Tavakoli, James A NichollsAbstract:Approximate Bayesian computation (ABC) is a powerful and widely used approach in inference of population history. However, the computational effort required to discriminate among alternative historical scenarios often limits the set that is compared to those considered more likely a priori. While often justifiable, this approach will fail to consider unexpected but well-supported population histories. We used a hierarchical tournament approach, in which subsets of scenarios are compared in a first round of ABC analyses and the winners are compared in a second analysis, to reconstruct the population history of an oak Gall Wasp, Synergus umbraculus (Hymenoptera, Cynipidae) across the Western Palaearctic. We used 4,233 bp of sequence data across seven loci to explore the relationships between four putative Pleistocene refuge populations in Iberia, Italy, the Balkans and Western Asia. We compared support for 148 alternative scenarios in eight pools, each pool comprising all possible rearrangements of four populations over a given topology of relationships, with or without founding of one population by admixture and with or without an unsampled "ghost" population. We found very little support for the directional "out of the east" scenario previously inferred for other Gall Wasp community members. Instead, the best-supported models identified Iberia as the first-regional population to diverge from the others in the late Pleistocene, followed by divergence between the Balkans and Western Asia, and founding of the Italian population through late Pleistocene admixture from Iberia and the Balkans. We compare these results with what is known for other members of the oak Gall community, and consider the strengths and weaknesses of using a tournament approach to explore phylogeographic model space.
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a new plagiotrochus mayr oak Gall Wasp species from taiwan hymenoptera cynipidae cynipini
Journal of Asia-pacific Entomology, 2016Co-Authors: Chang Ti Tang, Graham N Stone, Man-miao Yang, James A Nicholls, George MelikaAbstract:Abstract A new species of oak Gall Wasp, Plagiotrochus tarokoensis Tang and Melika sp. nov., is described from Taiwan. The species induces integral leaf Galls on Quercus tarokoensis (Fagaceae). Data on the diagnosis, distribution, and biology of the new species are given. This is the second known Plagiotrochus species from the Oriental region and the first one known to associate with the Ilex group of section Cerris oaks within Quercus linnaeus subgenus Quercus.
Lawrence M Hanks - One of the best experts on this subject based on the ideXlab platform.
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plant volatiles are behavioral cues for adult females of the Gall Wasp antistrophus rufus
Chemoecology, 2005Co-Authors: John F. Tooker, Amy L Crumrin, Lawrence M HanksAbstract:The purpose of this study was to identify plant volatiles that provide host location cues for adult females of the Gall Wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae). Larvae of this species inhabit flowering stems of the prairie perennial Silphium laciniatum L. (Asteraceae). Adult females responded to volatile compounds emitted by stems of S. laciniatum in field olfactometer bioassays. Plant volatiles were monoterpenes, including, in descending order of abundance, racemic α- and β-pinene (~50% “+” enantiomer for both), (+)-limonene, (−)-camphene, and β-myrcene. In laboratory bioassays, females responded to aeration extracts of plant stems, the full blend of synthetic monoterpenes, and the four-component blend of α-pinene, β-pinene, (+)-limonene, and (−)-camphene. This monoterpene blend apparently serves as an olfactory cue for host plant location for female A. rufus and is the first such cue to be reported for a cynipid Gall Wasp. Species-specific ratios of plant monoterpenes may provide cues for Gall Wasp females to distinguish between plant species and choose appropriate hosts for oviposition. The olfactometer and bioassay techniques developed for this research may be useful for field bioassays of other types of minute arthropods.
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stereochemistry of host plant monoterpenes as mate location cues for the Gall Wasp antistrophus rufus
Journal of Chemical Ecology, 2004Co-Authors: John F. Tooker, Lawrence M HanksAbstract:In spring, adult males of the Gall Wasp Antistrophus rufus L. emerge from inconspicuous Galls in stems of their host plant Silphium laciniatum L. and search for sites on stems where females will later emerge. The behavior of males suggests that they use olfaction rather than visual or tactile cues in searching for mates. In an earlier publication, we reported that Galls of A. rufus were associated with changes in enantiomeric ratios of α- and β-pinene emitted by plant stems, and hypothesized that monoterpene stereochemistry served as a mate location cue for adult males. Here, we support this hypothesis with bioassays that demonstrate that males can discriminate between Galled and unGalled stems, as well as between blends of synthetic monoterpenes with ratios of enantiomers representative of Galled and unGalled stems.
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altered host plant volatiles are proxies for sex pheromones in the Gall Wasp antistrophus rufus
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: John F. Tooker, Wilfried A Koenig, Lawrence M HanksAbstract:We describe a previously uncharacterized function for changes in plant chemistry induced by phytophagous insects: to provide cues for mate location. Larvae of the Gall Wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae) feed within inconspicuous Galls inside the flowering stems of the prairie perennials Silphium laciniatum L. and Silphium terebinthinaceum Jacquin (Asteraceae). Adult male A. rufus emerge before females and are challenged with locating mates that are sequestered within dead plant stems that occur in a matrix of dead vegetation. Allozyme studies revealed complete reproductive isolation between Wasp subpopulations in the two plant species. In laboratory bioassays, males responded only to their natal plant species, antennating the stem surface. Males from S. laciniatum also responded to hexane extracts of S. laciniatum stems, and extracts contained much higher concentrations of monoterpenes (α-pinene, β-pinene, and camphene) than did S. terebinthinaceum. Ratios of “+” and “−” enantiomers of α- and β-pinene approximated 50:50 for nonGalled S. laciniatum stems but strongly differed from 50:50 in Galled stems, with “+” and “−” enantiomers strongly dominant in different plants. In bioassays, male Wasps from S. laciniatum responded to a synthetic blend of the monoterpenes in enantiomeric ratios characteristic of Galled stems. Male A. rufus rely entirely on olfaction to locate females within stems in a complex prairie habitat, and Gall Wasps themselves apparently influence the plant to modify ratios of monoterpene enantiomers. These plant volatiles serve as a signal for males, acting as a sex pheromone proxy for females concealed within plant tissues.
John F. Tooker - One of the best experts on this subject based on the ideXlab platform.
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plant volatiles are behavioral cues for adult females of the Gall Wasp antistrophus rufus
Chemoecology, 2005Co-Authors: John F. Tooker, Amy L Crumrin, Lawrence M HanksAbstract:The purpose of this study was to identify plant volatiles that provide host location cues for adult females of the Gall Wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae). Larvae of this species inhabit flowering stems of the prairie perennial Silphium laciniatum L. (Asteraceae). Adult females responded to volatile compounds emitted by stems of S. laciniatum in field olfactometer bioassays. Plant volatiles were monoterpenes, including, in descending order of abundance, racemic α- and β-pinene (~50% “+” enantiomer for both), (+)-limonene, (−)-camphene, and β-myrcene. In laboratory bioassays, females responded to aeration extracts of plant stems, the full blend of synthetic monoterpenes, and the four-component blend of α-pinene, β-pinene, (+)-limonene, and (−)-camphene. This monoterpene blend apparently serves as an olfactory cue for host plant location for female A. rufus and is the first such cue to be reported for a cynipid Gall Wasp. Species-specific ratios of plant monoterpenes may provide cues for Gall Wasp females to distinguish between plant species and choose appropriate hosts for oviposition. The olfactometer and bioassay techniques developed for this research may be useful for field bioassays of other types of minute arthropods.
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stereochemistry of host plant monoterpenes as mate location cues for the Gall Wasp antistrophus rufus
Journal of Chemical Ecology, 2004Co-Authors: John F. Tooker, Lawrence M HanksAbstract:In spring, adult males of the Gall Wasp Antistrophus rufus L. emerge from inconspicuous Galls in stems of their host plant Silphium laciniatum L. and search for sites on stems where females will later emerge. The behavior of males suggests that they use olfaction rather than visual or tactile cues in searching for mates. In an earlier publication, we reported that Galls of A. rufus were associated with changes in enantiomeric ratios of α- and β-pinene emitted by plant stems, and hypothesized that monoterpene stereochemistry served as a mate location cue for adult males. Here, we support this hypothesis with bioassays that demonstrate that males can discriminate between Galled and unGalled stems, as well as between blends of synthetic monoterpenes with ratios of enantiomers representative of Galled and unGalled stems.
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altered host plant volatiles are proxies for sex pheromones in the Gall Wasp antistrophus rufus
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: John F. Tooker, Wilfried A Koenig, Lawrence M HanksAbstract:We describe a previously uncharacterized function for changes in plant chemistry induced by phytophagous insects: to provide cues for mate location. Larvae of the Gall Wasp Antistrophus rufus Gillette (Hymenoptera: Cynipidae) feed within inconspicuous Galls inside the flowering stems of the prairie perennials Silphium laciniatum L. and Silphium terebinthinaceum Jacquin (Asteraceae). Adult male A. rufus emerge before females and are challenged with locating mates that are sequestered within dead plant stems that occur in a matrix of dead vegetation. Allozyme studies revealed complete reproductive isolation between Wasp subpopulations in the two plant species. In laboratory bioassays, males responded only to their natal plant species, antennating the stem surface. Males from S. laciniatum also responded to hexane extracts of S. laciniatum stems, and extracts contained much higher concentrations of monoterpenes (α-pinene, β-pinene, and camphene) than did S. terebinthinaceum. Ratios of “+” and “−” enantiomers of α- and β-pinene approximated 50:50 for nonGalled S. laciniatum stems but strongly differed from 50:50 in Galled stems, with “+” and “−” enantiomers strongly dominant in different plants. In bioassays, male Wasps from S. laciniatum responded to a synthetic blend of the monoterpenes in enantiomeric ratios characteristic of Galled stems. Male A. rufus rely entirely on olfaction to locate females within stems in a complex prairie habitat, and Gall Wasps themselves apparently influence the plant to modify ratios of monoterpene enantiomers. These plant volatiles serve as a signal for males, acting as a sex pheromone proxy for females concealed within plant tissues.
Graham N Stone - One of the best experts on this subject based on the ideXlab platform.
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Gall Wasp transcriptomes unravel potential effectors involved in molecular dialogues with oak and rose
Frontiers in Physiology, 2019Co-Authors: Sebastien Cambier, Graham N Stone, Olivia Ginis, Sebastien J M Moreau, Philippe Gayral, Jack Hearn, David Giron, Elisabeth Huguet, Jeanmichel DrezenAbstract:To gain insight into Wasp factors that might be involved in the initial induction of Galls on woody plants, we performed high throughput (454) transcriptome analysis of ovaries and venom glands of two cynipid Gall Wasps, Biorhiza pallida and Diplolepis rosae, inducing Galls on oak and rose, respectively. De novo assembled and annotated contigs were compared to sequences from phylogenetically related parasitoid Wasps. The relative expression levels of contigs were estimated to identify the most expressed gene sequences in each tissue. We identify for the first time a set of maternally expressed Gall Wasp proteins potentially involved in the interaction with the plant. Some genes highly expressed in venom glands and ovaries may act to suppress early plant defense signaling. We also identify Gall Wasp cellulases that could be involved in observed local lysis of plant tissue following oviposition, and which may have been acquired from bacteria by horizontal gene transfer. We find no evidence of virus-related gene expression, in contrast to many non-cynipid parasitoid Wasps. By exploring Gall Wasp effectors, this study is a first step towards understanding the molecular mechanisms underlying cynipid Gall induction in woody plants, and the recent sequencing of oak and rose genomes will enable study of plant responses to these factors.
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tournament abc analysis of the western palaearctic population history of an oak Gall Wasp synergus umbraculus
Molecular Ecology, 2017Co-Authors: Graham N Stone, Karsten Schönrogge, George Melika, Sarah C White, Gyorgy Csoka, Serap Mutun, Zsolt Penzes, Ebrahim S Sadeghi, Majid Tavakoli, James A NichollsAbstract:Approximate Bayesian computation (ABC) is a powerful and widely used approach in inference of population history. However, the computational effort required to discriminate among alternative historical scenarios often limits the set that is compared to those considered more likely a priori. While often justifiable, this approach will fail to consider unexpected but well-supported population histories. We used a hierarchical tournament approach, in which subsets of scenarios are compared in a first round of ABC analyses and the winners are compared in a second analysis, to reconstruct the population history of an oak Gall Wasp, Synergus umbraculus (Hymenoptera, Cynipidae) across the Western Palaearctic. We used 4,233 bp of sequence data across seven loci to explore the relationships between four putative Pleistocene refuge populations in Iberia, Italy, the Balkans and Western Asia. We compared support for 148 alternative scenarios in eight pools, each pool comprising all possible rearrangements of four populations over a given topology of relationships, with or without founding of one population by admixture and with or without an unsampled "ghost" population. We found very little support for the directional "out of the east" scenario previously inferred for other Gall Wasp community members. Instead, the best-supported models identified Iberia as the first-regional population to diverge from the others in the late Pleistocene, followed by divergence between the Balkans and Western Asia, and founding of the Italian population through late Pleistocene admixture from Iberia and the Balkans. We compare these results with what is known for other members of the oak Gall community, and consider the strengths and weaknesses of using a tournament approach to explore phylogeographic model space.
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a new plagiotrochus mayr oak Gall Wasp species from taiwan hymenoptera cynipidae cynipini
Journal of Asia-pacific Entomology, 2016Co-Authors: Chang Ti Tang, Graham N Stone, Man-miao Yang, James A Nicholls, George MelikaAbstract:Abstract A new species of oak Gall Wasp, Plagiotrochus tarokoensis Tang and Melika sp. nov., is described from Taiwan. The species induces integral leaf Galls on Quercus tarokoensis (Fagaceae). Data on the diagnosis, distribution, and biology of the new species are given. This is the second known Plagiotrochus species from the Oriental region and the first one known to associate with the Ilex group of section Cerris oaks within Quercus linnaeus subgenus Quercus.
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native and introduced parasitoids attacking the invasive chestnut Gall Wasp dryocosmus kuriphilus
Eppo Bulletin, 2007Co-Authors: Alexandre Aebi, Karsten Schönrogge, George Melika, Alberto Alma, Ambra Quacchia, Graham N StoneAbstract:The globally invasive chestnut Gall Wasp Dryocosmus kuriphilus was recently reported in Italy and threatens European chestnut orchards and native forests. Of Chinese origin, this species has invaded Japan, Korea, the USA, Nepal and Europe and in each region it has been attacked by parasitoids exploiting oak Gall Wasps. Classical biological control using the parasitoid Torymus sinensis (Hymenoptera: Torymidae) successfully reduced infestation in Japan. Subsequent work in Japan and Korea showed this parasitoid to represent a poorly understood and biologically diverse species complex. Following its success in Japan, T. sinensis was released in Italy in 2005. A growing appreciation of the taxonomic and ecological complexity of the T. sinensis complex in Japan and Korea has stimulated ongoing DNA-based work on relationships and interbreeding of species in this group. Oak cynipid parasitoids provide potential for native augmentative or conservation biological control of D. kuriphilus in Europe. Exploitation of this potential requires improved understanding of the taxonomy of these parasitoids, particularly of morphologically highly conserved lineages such as Eurytoma and Eupelmus in which recognised species may contain many cryptic lineages. There is a growing need for a molecular survey of the communities centered on chestnut and oak Gall Wasps to: (1) ascertain the identity of T. sinensis lineages released in Italy (2) track the dispersal of T. sinensis in the native community, either in its original form or as hybrids with native species (3) identify possible biological control agents in the native parasitoid community.
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comparative phylogeography across two trophic levels the oak Gall Wasp andricus kollari and its chalcid parasitoid megastigmus stigmatizans
Molecular Ecology, 2005Co-Authors: Alexander Hayward, Graham N StoneAbstract:Insect parasitoids are important components of many terrestrial ecosystems. However, relatively little is known about the mechanisms responsible for structuring their populations. Here we investigate the ability of Megastigmus stigmatizans , an oak Gall Wasp parasitoid, to track its host Andricus kollari over two different timescales, and examine its current population structure across a divide in host population structure. The divide represents a transition in Gall Wasp host-plant species and offers the opportunity to examine whether the split, which divides Gall Wasp populations, manifests itself in the next trophic level. Analysis of mitochondrial haplotype data for parasitoid and host reveals: (i) A similar phylogeographic population structure for both, with Iberian populations more derived with respect to more eastern populations. (ii) It is likely that the host colonized the Iberian refuge earlier than the parasitoid, probably by at least one glacial cycle. (iii) Recent range expansion of central European host populations northwards has resulted in pursuit by parasitoids from the same geographic origin. (iv) In addition, Iberian parasitoid populations have crossed a major divide in host population structure to invade northern Europe. Such human-facilitated escape from natural refugial distributions may have important implications for the composition and structure of northern European Gall Wasp communities.
