Use this URL to cite or link to this record in EThOS:
Title: Impact and management of invasive plant species : a food web approach
Author: Carvalheiro, Luisa Mafalda Gigante
ISNI:       0000 0001 3523 8922
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2007
Availability of Full Text:
Access from EThOS:
Access from Institution:
Invasive plants can significantly affect ecosystems. While their impacts on plant populations are widely reported, data on how higher trophic levels are affected by those changes are scarce. The work presented here aims to provide further insights for the study of impacts and management of invasive species, using food webs as a tool for assessing and predicting consequences of habitat disruptions. The first question I address in this thesis is how the removal of alien plant species from a UK site of conservation interest affects the pollination of a rare plant Trinia glauca (Apiaceae). A food web approach was used to identify the main pollinators of this rare plant species, and to understand how this rare plant interacts indirectly with the introduced species present in the study area via shared flower visitors. I simulated the likely consequences of removal of alien plants on T. glauca pollination, any effects being mediated by shared pollinators. This approach was used to reveal the potential negative impacts of habitat management (here alien plant removal) on the native plants. Secondly, I consider how the impact of an invasive weed of UK heathlands, Gaultheria shallon, propagates through food webs affecting plants, herbivores and parasitoids. Using a quantitative food web approach, I found that diet breadth influences the propagation of impacts, leading to changes in the food web structure. Specialist consumers which had all their resource species affected by G. shallon were the most affected by the invasive plant. I consider the implications of these results for conservation ecology and highlight the importance of extending impact evaluation to higher trophic levels as well as considering trophic diversity within levels, for a full evaluation of the consequences of disturbances. Finally, I evaluated the indirect non-target impacts of a management measure considered safe and environmentally friendly: the use of highly specific weed biocontrol agents. I used 17 replicate food-webs to demonstrate that natural enemies are shared between an abundant successfully established biocontrol agent, Mesoclanis polana, and seed herbivore species from native plants. I found that the agent abundance is associated with local insect biodiversity losses, apparent competition being the most likely explanation. Thus, my study suggests that food webs are a useful tool for assessing and predicting. consequences of plant invasion and their management.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available