No description available.

No description available.

Host specificity of tropical bark and ambrosia beetles was surveyed by rearing the beetles from 13 host trees in a lowland rainforest in Papua New Guinea. Ploeophagous bark beetles show narrow host specificity (usually family-level) typical for herbivorous insects, fungus-growing ambrosia beetles display almost no host fidelity. In both groups of species, the local diversity of plants is unlikely to have played a role in the clade diversification. The ambrosia symbiosis (scolytine beetles and fungi) is shown to be less specific than previously assumed, based on a discovery of new association between Scolytodes unipunctatus (genus of phloem feeders) and three unrelated groups of ambrosia fungi. The hypothesis that apparent polyphagy may conceal specialized populations within a species of a herbivore is tested for Homona mermerodes (Lepidoptera, Tortricidae). The haplotype diversity of the species show no congruence with host plants or geographic origin, confirming polyphagy of the species.

Ambrosia artemisiifolia L. (Asteraceae) est une plante annuelle originaire d'Amérique du Nord, introduite accidentellement à la fin du 19ème siècle en Europe. En France, cette espèce envahissante est à l'origine d'importants problèmes de santé publique causés par son pollen allergisant. C'est également une adventice problématique dans certaines cultures de printemps. Plus généralement, l'espèce colonise tous types d'habitats perturbés par l'homme. Son développement dans les milieux naturels semble cependant limité aux habitats régulièrement perturbés (grèves des rivières).<br />L'objectif de ce travail de thèse a été d'étudier à travers une approche multidisciplinaire, les différentes caractéristiques de l'espèce, tant biologiques, génétiques, qu'écologiques, ainsi que les caractéristiques des communautés envahies, pouvant permettre d'expliquer le succès de son envahissement en France.<br />Une synthèse bibliographique a été réalisée sur les différents paramètres impliqués dans les phénomènes d'invasions biologiques et sur les connaissances actuelles du modèle étudié, A. artemisiifolia.<br />Les différents traits d'histoire de vie de l'espèce ont révélé une variabilité considérable, en particulier au niveau des semences, ce qui suggère l'existence d'une stratégie adaptée à la colonisation d'environnements variables. L'importante plasticité phénotypique d'A. artemisiifolia mise en évidence, explique en partie le succès de cet envahisseur. La dynamique générale des populations (taux d'accroissement) est également différente entre habitats. Le facteur limitant la colonisation ou le maintien des populations est sans conteste la fermeture du milieu. De plus, la présence de mycorhizes à arbuscules dans les communautés envahies serait également un des facteurs susceptibles de faciliter le processus d'envahissement de l'espèce.<br />D'autre part, le potentiel d'envahissement de cette espèce peut s'expliquer par les niveaux de diversité génétique très élevés des populations natives et introduites, observés à l'aide de différents marqueurs moléculaires (ADNcp, AFLP). Ces résultats suggèrent également que l'espèce a été introduite à de multiples reprises, à partir de différentes sources et avec un nombre important de fondateurs. <br />Enfin, nos résultats montrent qu'A. artemisiifolia possède une amplitude écologique très large et qu'elle n'est pas spécifiquement inféodée à un groupement végétal particulier. L'espèce est donc capable de coloniser des environnements écologiquement différents et peut potentiellement accroître son aire de distribution de manière considérable.<br />Les connaissances acquises au cours de cette thèse montrent que l'invasion d'A. artemisiifolia est un phénomène multifactoriel. L'envahissement de cette espèce dépend avant tout des conditions rencontrées lors de son processus d'introduction et de colonisation (habitats perturbés, dispersion anthropique). Son caractère généraliste lui permet ensuite de pouvoir répondre de manière optimale aux conditions environnementales rencontrées. Nos résultats suggèrent que dans le contexte actuel, A. artemisiifolia présente un potentiel d'envahissement considérable en France comme dans le reste de l'Europe.

Common ragweed (Ambrosia artemisiifolia L., Asteraceae) is an annual herbacious weed that is a troublesome pest in carrot fields of Southwestern Quebec. Over the past decade, ragweed has shown resistance to linuron, the only herbicide that is registered for post-emergence control of this weed in carrots. In this research, the degree of resistance to linuron was investigated for a ragweed biotype collected from a carrot field in Sherrington, Quebec, where a decreased performance of linuron had been noted. This biotype showed a linuron resistance ratio (I50) of 9.09, when compared with ragweed plants collected from a field never sprayed with this herbicide. The fungal pathogen Phoma sp., which had been initially isolated from diseased ragweed leaves in 1993, was considered as a potentially effective biological agent for the control of common ragweed. The pathogenicity of Phoma sp. was re-evaluated during the current research. This fungus was found not to have any appreciable virulence towards common ragweed; it is likely that virulence was lost during storage. Hence, twenty other fungal species were isolated from diseased common ragweed plants and assayed to determine their potential as biological agents against this noxious weed. Varying dew periods, temperatures, spore concentrations, host growth stages, and different types of carrier were evaluated. Only isolates ATT#9, INNA4a, INNA4b, ATT#10, ISO#65, and ISO#68 were able to induce lesions on ragweed foliage at spore concentrations of 106 to 107 spores ml-1, but only after an extended dew period of 48 hrs. No interaction effects on the degree of ragweed control were found when combining five fungal isolates and the insect, Ophraella communa LeSage. However, a possible interactive effect was detected when the fungal isolate ISO#65 and linuron were used in combination.

<div>Native and invasive bark and ambrosia beetles threaten the health and productivity of natural and planted forests worldwide. Management of these pests relies on semiochemical-based tactics, but these are often ineffective at monitoring for incipient populations or decreasing pest populations. The role of fungal and non-host volatiles in colonization behavior remains unknown for many important bark and ambrosia beetle species, thereby hindering their control. In this dissertation, I tested the hypothesis that fungal and tree-associated volatiles influence the host colonization behavior of bark and ambrosia beetles that affect hardwood trees. This work describes the identification of novel fungal and host-associated semiochemicals that may aid in future management of these important pests.</div><div><br></div><div>In Chapter 1, I review the current literature describing the volatile chemical ecology of bark and ambrosia beetles that inhabit hardwood trees. A review of groups with numerous identified semiochemicals, as well as considerations for future research is included.</div><div><br></div><div>In Chapter 2, I test the hypothesis that host colonization by the peach bark beetle (Phloeotribus liminaris) is chemically mediated by compounds associated with infested hosts. I found that benzaldehyde mediates colonization by the peach bark beetle, and that that benzaldehyde lures are effective attractants in field-trapping studies.</div><div><br></div><div>In Chapter 3, I test the hypothesis that ambrosia beetle attraction to host stress compounds can be modified by symbiotic fungal volatiles. I found that for three species of invasive ambrosia beetles individual fungal volatiles act as repellents, with species-specific differences in response to different compounds.</div><div><br></div><div>In Chapter 4, I test the hypothesis that attraction of the walnut twig beetle (Pityophthorus juglandis) to its pheromone lure can be enhanced by symbiotic fungal volatiles. I found that symbiotic fungal volatiles consistently enhance attraction of the beetles to their fungus, while one symbiotic fungal volatile of ambrosia beetle species repelled the walnut twig beetle.</div><div><br></div><div>In Chapter 5, I summarize results from each of the chapters and discuss patterns observed in the response to fungal and host-associated volatiles among the focal bark and ambrosia beetle species. I also discuss future research needs and directions to continue development of the knowledge surrounding scolytine chemical ecology and management of these pest beetle species.</div>

No description available.

The Forgiveness Project includes a critical introduction that defines the author’s approach to the short-short form as well as an explanation of how historiographical metafiction can work to memorialize. The first section contains primarily short-short stories that address the themes of motherhood, small tyrannies, happy liars, caregiving and the clichés of grief. A collection of linked short stories follows, revolving around elusive forgiveness. On the night of July 17, 1977, Juanita Lee, a bridge tender in South Florida, was abducted by two men and executed in the Everglades to silence her opposition to the demolition of an Intracoastal Waterway bridge. Twenty-two years later her daughter, Jill, now a Washington D.C. lobbyist who views the world through the cynical lens of her life’s work, is confronted with a plea for forgiveness via an organization called “The Forgiveness Project,” representing one of her mother’s killers.

No description available.

No description available.