Abstract/Summary

Tree diseases have the potential to cause severe disruption to landscapes and ecosystems by reducing the number of healthy trees within an ecosystem, which act as foundations for a plethora of other species. The mechanism behind the spread of plant pathogens which cause such diseases is variable across pathosystems but is less understood for tree diseases. Acute Oak Decline (AOD) is a disease of oak trees which is fast acting and can result in the death of trees within a few years from the presentation of symptoms. AOD is believed to be caused by the action of a few pathogenic bacteria, however the mechanism behind the spread of these bacteria is not fully understood. The close association between some woodland bird species and oak trees allows for an ideal system where the wider ecological impacts of AOD can be investigated. In this thesis the current knowledge of plant pathogens and their vectors is explored, finding significant gaps in the research around tree diseases and vertebrate vectors. The role of woodland birds as vectors of the bacteria of AOD is then explored, using both culture based and molecular techniques. The results from this work allow me to explore variations in the microbial communities of birds in areas with differing levels of AOD. In order to examine wider ecosystem impacts of AOD, insect oak herbivory was quantified, along with bird breeding success across areas of woodland with differing AOD severity levels, finding higher insect herbivory levels but lower bird breeding intention in areas with higher AOD. Overall, this thesis utilises a variety of techniques to explore the wider ecosystem impacts of AOD and gives us an insight into how tree diseases may have knock-on consequences for other organisms within a habitat.