Be phenomenon in open clusters: Results from a survey of emission-line stars in young open clusters

Emission-line stars in young open clusters are identified to study their properties, as a function of age, spectral type and their evolutionary state. 207 open star clusters were observed using slitless spectroscopy method and 157 emission stars were identified in 42 clusters. We have found 54 new emission-line stars in 24 open clusters, out of which 19 clusters are found to house emission stars for the first time. About 20% clusters harbour emission stars. The fraction of clusters housing emission stars is maximum in both the 0--10 and 20--30 Myr age bin ($\sim$ 40% each) and in the other age bins, this fraction ranges between 10% -- 25%, upto 80 Myr. We have used optical colour magnitude diagram (CMD) along with Near-IR Colour-Colour diagram (NIR CCDm) to classify the emission stars into Classical Be (CBe) stars and Herbig Be (HBe) stars. Most of the emission stars in our survey belong to CBe class ($\sim$ 92%) while a few are HBe stars ($\sim$ 6%) and HAe stars ($\sim$1%). The CBe stars are located all along the MS in the optical CMDs of clusters of all ages, which indicates that the Be phenomenon is unlikely due to core contraction near the turn-off. Most of the clusters which contain emission stars are found in Cygnus, Perseus & Monoceros region of the Galaxy, which are locations of active star formation. The distribution of CBe stars as a function of spectral type shows peaks at B1-B2 and B6-B7. Our results indicate there could be two mechanisms responsible for the CBe phenomenon. Some are born CBe stars (fast rotators), as indicated by their presence in clusters younger than 10 Myr. Some stars evolve to CBe stars, as indicates by the enhancement in the fraction of clusters with CBe stars in the 20-30 Myr age bin.Comment: 54 pages, 18 figures, Submitted to MNRA

Field Assessment of the Host Range of Aculus mosoniensis (Acari: Eriophyidae), a Biological Control Agent of the Tree of Heaven (Ailanthus altissima)

Tree of heaven (Ailanthus altissima) is a fast-growing deciduous tree native to China, considered a serious invasive species worldwide, with several socio-economic and ecological impacts attributed to it. Chemical and mechanical methods have limited efficacy in its management, and biological controls may offer a suitable and sustainable option. Aculus mosoniensis (Ripka) is an eriophyid mite that has been recorded to attack tree of heaven in 13 European countries. This study aims to explore the host range of this mite by exposing 13 plant species, selected either for their phylogenetic and ecological similarity to the target weed or their economic importance. Shortly after inoculation with the mite, we recorded a quick decrease in mite number on all nontarget species and no sign of mite reproduction. Whereas, after just one month, the population of mites on tree of heaven numbered in the thousands, irrespective of the starting population, and included both adults and juveniles. Significantly, we observed evidence of damage due to the mite only on target plants. Due to the specificity, strong impact on the target, and the ability to increase its population to high levels in a relatively short amount of time, we find A. mosoniensis to be a very promising candidate for the biological control of tree of heaven

Modulations in the radio light curve of the Type IIb Supernova 2001ig: Evidence for a Wolf-Rayet binary progenitor?

We describe the radio evolution of SN 2001ig in NGC 7424, from 700 days of multi-frequency monitoring with the Australia Telescope Compact Array (ATCA) and the Very Large Array (VLA). We find that deviations of the radio light curves at each frequency from the standard "minishell" model are consistent with density modulations in the circumstellar medium (CSM), which seem to recur with a period near 150 days. One possibility is that these are due to enhanced mass-loss from thermal pulses in an AGB star progenitor. A more likely scenario however is that the progenitor was a Wolf-Rayet star, whose stellar wind collided with that from a massive hot companion on an eccentric 100 day orbit, leading to a regular build-up of CSM material on the required time and spatial scales. Recent observations of "dusty pinwheels" in Wolf-Rayet binary systems lend credibility to this model. Since such binary systems are also thought to provide the necessary conditions for envelope-stripping which would cause the Wolf-Rayet star to appear as a Type Ib/c supernova event rather than a Type II, these radio observations of SN 2001ig may provide the key to linking Type Ib/c SNe to Type IIb events, and even to some types of Gamma-Ray Bursts.Comment: 10 pages, MNRAS, accepte

Challenges for molecular neuroimaging with MRI

Magnetic resonance (MRI)-based molecular imaging methods are beginning to have impact in neuroscience. A growing number of molecular imaging agents have been synthesized and tested in vitro, but so far relatively few have been validated in the brains of live animals. Here, we discuss key challenges associated with expanding the repertoire of successful molecular neuroimaging approaches. The difficulty of delivering agents past the blood-brain barrier (BBB) is a particular obstacle to molecular imaging in the central nervous system. We review established and emerging techniques for trans-BBB delivery, including intracranial infusion, BBB disruption, and transporter-related methods. Improving the sensitivity with which MRI-based molecular agents can be detected is a second major challenge. Better sensitivity would in turn reduce the requirements for delivery and alleviate potential side effects. We discuss recent efforts to enhance relaxivity of conventional longitudinal relaxation time (T1) and transverse relaxation time (T2) MRI contrast agents, as well as strategies that involve amplifying molecular signals or reducing endogenous background influences. With ongoing refinement of imaging approaches and brain delivery methods, MRI-based techniques for molecular-level neuroscientific investigation will fall increasingly within reach.Raymond and Beverley Sackler FoundationNational Institutes of Health (U.S.) (R01-DA28299)National Institutes of Health (U.S.) (DP2-OD2441

Cryptic host-associated and frequency-dependent patterns of host species selection of a candidate weed biological control agent in its native range

At least nine species of European hawkweeds in the genus Pilosella Vaill. (Asteraceae) are invasive in western North America, where they are a detriment to natural and managed lands and have vast economic impacts. A promising candidate biological control (biocontrol) agent for multiple species of Pilosella is the gall inducing wasp Aulacidea pilosellae Kieffer (Hymenoptera: Cynipidae). Initial studies of this candidate agent revealed the potential for two biotypes of the insect that differed in physiological host range, voltinism, and reproductive mode. It was hypothesized that these differences were related to geographic separation of the populations and it was further observed, within one subset of the distribution, that different host species were being used at nearby sites, despite similar host species being present. The overarching goal of this thesis was to increase the understanding of the patterns of host species use by A. pilosellae in order to inform the biocontrol programme for invasive Pilosella hawkweeds. The specific objectives were to (i) test the hypothesis that A. pilosellae has definitive preferences for species of Pilosella within its ecological host range, (ii) further quantify the ecological host range of A. pilosellae by conducting systematic surveys across a broad geographic distribution, and (iii) test the hypothesis that differences between the purported biotypes were due to cryptic genetic differentiation, predicted to be based primarily on geographic location of populations and secondly on host-association. By utilizing an integrative approach of thorough and widespread field surveys and molecular methodologies, this thesis presents findings that substantially increase the understanding of patterns of host species use by A. pilosellae in its native range. Specifically, (i) the hypothesis of host preferences of A. pilosellae is rejected in favor of frequency-dependent host species selection, (ii) five species of Pilosella invasive in North America are confirmed as hosts of A. pilosellae in its native range and (iii) the hypothesis that cryptic genetic differentiation exists within the species A. pilosellae was supported. However, the prediction that differentiation was based primarily on geographic separation was rejected in favor of differentiation based on a combination of disjunct hostassociations, infection with the bacterial endosymbiont Wolbachia, and to a lesser extent, on geography.Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)Graduat

Host shifts in herbivorous insects: testing model predictions for the earliest stages of ecological speciation

<p>This poster presents preliminary data from a field study that tests the hypothesis that specialists are most likely to exploit novel host individuals that most closely resemble their ancestral host.</p

Ovipositor characteristics differ between two parasitoids (Hymenoptera, Figitidae) of Drosophila suzukii (Diptera, Drosophilidae) in an adventive landscape

Different ovipositor characteristics among parasitoid species that share similar niches are associated with different wasp life histories and selective pressures. The length of wasp ovipositors, for example, can determine the accessibility of hosts that feed at different depths within food substrates. Two parasitoids, Ganaspis brasiliensis and Leptopilina japonica (Hymenoptera, Figitidae), which attack Drosophila suzukii (Diptera, Drosophilidae) in their native range, have been investigated for their suitability for the global biological control of the small fruit pest. Despite their sympatry in microhabitat, the parasitoids have differing host ranges, and D. suzukii parasitism rates by each parasitoid species appear to depend on the fruit species occupied by the host species. Adventive populations of both parasitoids have been detected in the Pacific Northwest of Canada and the United States where they can be found parasitizing D. suzukii larvae in crop and non-crop fruits. We dissected and measured the ovipositors of parasitoids reared from three species of fresh fruits at three sites in southwestern British Columbia, Canada, and investigated the influence of parasitoid species, fruit type, and collection site on ovipositor characteristics. We found that ovipositor length differed markedly between the two parasitoid species and between sites while ovipositor width, and stoutness, differed only between the two parasitoid species, but did not vary among sites or fruit hosts. We discuss how ovipositor morphology traits could be associated with differences in life history and host ranges in the two parasitoid species

Response of the Pacific Coast wireworm, Limonius canus, and the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), to insecticide-treated wheat seeds in a soil bioassay

Larvae of the dusky wireworm, Agriotes obscurus, and the Pacific Coast wireworm, Limonius canus, were exposed to germinated, insecticide-treated wheat seeds in a soil-filled bioassay in 2005 and 2006. Position in the bioassay and contact and/or repellence behaviour towards the seeds were recorded every 5 min for 3 or 5 h. Wireworm health was recorded for 70 or 126 d after exposure. Seeds were treated with the fungicides Dividend XLRTA (difenoconazole, mefenoxam) or Raxil MD (tebuconazole, metalaxyl), and/or the insecticides Vitavax Dual (lindane), Poncho 600F (clothianidin), Cruiser 350FS (thiamethoxam), Admire 240FS (imidacloprid), Gaucho 480FL (imidacloprid), Tefluthrin 20CS (tefluthrin), or Tefluthrin-Cruiser combinations. Most wireworms (> 80%) came into contact with the seeds in all treatments. Wireworms generally remained in contact throughout the observation period in the control treatments (Dividend, Raxil, untreated seeds). Unless moribund, wireworms were repelled after brief ( 80 %) sont entrés en contact avec les semences dans tous les traitements. Ils sont généralement demeurés en contact avec les semences durant toute la période d’observation dans les traitements témoins (Dividend, Raxil, semences non traitées). Les larves ont été repoussées après un bref contact (< 20 min) dans tous les traitements de Tefluthrin, sauf si elles étaient moribondes. La majorité des vers fil-de-fer se sont remis de la morbidité induite par le contact avec les semences à l’intérieur de 21 h et n’ont pas fait de rechute, à l’exception des larves de L. canus exposées au Cruiser et de quelques larves de A. obscurus exposées aux insecticides Gaucho et Admire. Le taux de mortalité était bas (< 50 %) dans tous les traitements sauf pour les larves de L. canus exposées au Cruiser à 15 et 30 g m.a. 100 kg-1 graine (60 et 75 %, respectivement). Le taux de mortalité était significativement plus bas lorsque les larves de L. canus étaient exposées à des combinaisons Tefluthrin-Cruiser que lorsqu’elles étaient exposées seulement au Cruiser. Ces résultats suggèrent que pour évaluer l’efficacité des insecticides à lutter contre les populations de vers fil-de-fer, une observation directe de leur comportement ainsi qu’une évaluation à long terme de leur état de santé sont nécessaires. L’impact de la répulsion et de la morbidité causées par les insecticides sur la lutte aux vers fil-de-fer dans les champs est également abordé

Response of the Pacific Coast wireworm, Limonius canus, and the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), to insecticide-treated wheat seeds in a soil bioassay

Larvae of the dusky wireworm, Agriotes obscurus, and the Pacific Coast wireworm, Limonius canus, were exposed to germinated, insecticide-treated wheat seeds in a soil-filled bioassay in 2005 and 2006. Position in the bioassay and contact and/or repellence behaviour towards the seeds were recorded every 5 min for 3 or 5 h. Wireworm health was recorded for 70 or 126 d after exposure. Seeds were treated with the fungicides Dividend XLRTA (difenoconazole, mefenoxam) or Raxil MD (tebuconazole, metalaxyl), and/or the insecticides Vitavax Dual (lindane), Poncho 600F (clothianidin), Cruiser 350FS (thiamethoxam), Admire 240FS (imidacloprid), Gaucho 480FL (imidacloprid), Tefluthrin 20CS (tefluthrin), or Tefluthrin-Cruiser combinations. Most wireworms (> 80%) came into contact with the seeds in all treatments. Wireworms generally remained in contact throughout the observation period in the control treatments (Dividend, Raxil, untreated seeds). Unless moribund, wireworms were repelled after brief ( 80 %) sont entrés en contact avec les semences dans tous les traitements. Ils sont généralement demeurés en contact avec les semences durant toute la période d’observation dans les traitements témoins (Dividend, Raxil, semences non traitées). Les larves ont été repoussées après un bref contact (< 20 min) dans tous les traitements de Tefluthrin, sauf si elles étaient moribondes. La majorité des vers fil-de-fer se sont remis de la morbidité induite par le contact avec les semences à l’intérieur de 21 h et n’ont pas fait de rechute, à l’exception des larves de L. canus exposées au Cruiser et de quelques larves de A. obscurus exposées aux insecticides Gaucho et Admire. Le taux de mortalité était bas (< 50 %) dans tous les traitements sauf pour les larves de L. canus exposées au Cruiser à 15 et 30 g m.a. 100 kg-1 graine (60 et 75 %, respectivement). Le taux de mortalité était significativement plus bas lorsque les larves de L. canus étaient exposées à des combinaisons Tefluthrin-Cruiser que lorsqu’elles étaient exposées seulement au Cruiser. Ces résultats suggèrent que pour évaluer l’efficacité des insecticides à lutter contre les populations de vers fil-de-fer, une observation directe de leur comportement ainsi qu’une évaluation à long terme de leur état de santé sont nécessaires. L’impact de la répulsion et de la morbidité causées par les insecticides sur la lutte aux vers fil-de-fer dans les champs est également abordé

Transcriptomics-Based Approach Identifies Spinosad-Associated Targets in the Colorado Potato Beetle, Leptinotarsa decemlineata

The Colorado potato beetle Leptinotarsa decemlineata is an insect pest that threatens potato crops globally. The primary method to control its damage on potato plants is the use of insecticides, including imidacloprid, chlorantraniliprole and spinosad. However, insecticide resistance has been frequently observed in Colorado potato beetles. The molecular targets and the basis of resistance to imidacloprid and chlorantraniliprole have both been previously quantified. This work was undertaken with the overarching goal of better characterizing the molecular changes associated with spinosad exposure in this insect pest. Next-generation sequencing was conducted to identify transcripts that were differentially expressed between Colorado potato beetles exposed to spinosad versus control insects. Results showed several transcripts that exhibit different expression levels between the two conditions, including ones coding for venom carboxylesterase-6, chitinase 10, juvenile hormone esterase and multidrug resistance-associated protein 4. In addition, several microRNAs, such as miR-12-3p and miR-750-3p, were also modulated in the investigated conditions. Overall, this work reveals a molecular footprint underlying spinosad response in Colorado potato beetles and provides novel leads that could be targeted as part of RNAi-based approaches to control this insect pest