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Research project (§ 26 & § 27)
Duration : 2015-12-02 - 2019-12-01

Ash dieback caused by the ascomycete Hymenoscyphus fraxineus has spread recently all over Austria. This disease has caused severe damage on ash trees, and can cause yield loss, dieback and even dieback of affected trees. This disease is currently causing major changes in the composition and ecology of hardwood forests in Austria. The management of ash has more or less stopped, as only old trees are harvested but regeneration is absent. However, also in highly affected stands apparently resistant trees are detected regularly. These trees usually show only few or no symptoms of the disease and probably have a high level of resistance against the pathogen. Up to 5% of the clones in Austrian seed orchards appear to be resistant to the disease to a certain degree. International research has provided evidence that a large part of this resistance has a genetic basis. Based on these results efforts to select resistant clones seem very promising to maintain ash as one of the main hardwood species in Austria. The basis for such an endeavour is the collection of a large number of resistant clones from all over Austria, both to be able to select the best clones, but also to maintain genetic diversity in the species. The goal of the proposed project is the selection of several hundred resistant mother clones to conserve the genetic diversity of the species. The breeding value of the selected mother trees will be calculated based on the performance of single tree offspring in a common garden experiment. In a further step male trees (putative father) of these offspring will be identified by paternity analysis to be able also to select male ash trees for a future seed orchard. Both the best mother and father trees are to be propagated by grafting and cuttings, to preserve their genetic information. This selection of highly resistant clones with superior resistance against ash dieback will enable the set-up of new ash clone seed orchards. Vegetatively propagated plants shall also be provided to end users, to provide resistant reproductive material to forest managers, as a direct output of the project.
Research project (§ 26 & § 27)
Duration : 2016-05-10 - 2017-02-05

Speciation is a fundamental evolutionary process responsible for the great diversity of life on Earth. Main factors contributing to the evolution of reproductive isolation are geographic and ecological isolation. However, oft-forgotten and controversially discussed players in the speciation process of insects are reproduction-manipulating endosymbiotic bacteria of the genus Wolbachia that can form pre- and postzygotic barriers in infected insect populations. The multiply infected Rhagoletis fruit flies are an excellent system to study such effects as the evolutionary history of this genus involves a number radiations with different geographic modes, ranging from classic allopatric divergence to sympatric speciation via host plant shifting. Aim of this proposal is to evaluate the contribution of Wolbachia to speciation in different Rhagoletis species utilizing on-site research at the highly complex structured North American fruit fly populations. The research objective will be accomplished by analyzing Wolbachia strains from different Rhagoletis species groups that have undergone allopatric (e.g., R. suavis group) vs. sympatric (e.g., R. pomonella group) speciation. Following the broadly accepted theory that bacterial reproductive isolation almost always evolves in allopatry, I hypothesize that sympatrically derived species with extant gene flow will share the same strains of Wolbachia while allopatric species will possess different strains. I will test this hypothesis by the characterization of different Rhagoletis populations. Further, Wolbachia strains in parasitoid wasps attacking Rhagoletis flies will be characterized as possible vector of horizontal Wolbachia transmission between Rhagoletis species. This will give new insights into routes of horizontal transmission between different species and the evolution of Wolbachia in geographically separated populations with possible influences into speciation. Going beyond the capabilities of the established MLST system for strain discrimination, a combination of Sanger and next generation high throughput sequencing will be adapted to perform a high resolution characterization of this bacteria. Additionally the Rhagoletis species and their parasitoids will be screened for other bacterial endosymbionts influencing the host’s reproduction. Verifying an active role of Wolbachia in reproductive isolation and Rhagoletis speciation will ultimately require breeding of flies that are depleted of the bacteria to determine the extent that fertility is restored between flies. Thus, a secondary objective of the current proposal is to develop and establish protocols for curing Rhagoletis of Wolbachia, allowing follow-up manipulative studies in the future to confirm a direct connection of Wolbachia with fly reproductive isolation.
Research project (§ 26 & § 27)
Duration : 2015-12-01 - 2018-03-31

The knowledge of the actual weather conditions and the wind speed at the time of beetle swarming from the release site and their recapture in the various traps will allow evaluating the influence of single weather parameters on beetle flight directions and distances depending on the topographic situation of the locality. By combining the data from different sites under different topographic and weather conditions, a model will be developed which may be used to forecast the beetle’s dispersal from infested sites to vulnerable sites predisposed for new infestation by including weather forecast data for the near future.

Supervised Theses and Dissertations