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dc.contributor.authorGrant-Hoffman, Madeline N.
dc.date.accessioned2018-08-06T20:49:52Z
dc.date.available2018-08-06T20:49:52Z
dc.date.issued2009
dc.identifier.urihttp://hdl.handle.net/11122/8984
dc.descriptionThesis (Ph.D.) University of Alaska Fairbanks, 2009
dc.description.abstractInvasive rats (Rattus exulans, R. rattus, and R. norvegicus) affect vegetation directly through herbivory and indirectly through predation on burrowing seabirds (Procellariiformes: petrels, prions, shearwaters). These seabirds affect vegetation through allochthonous inputs and physical disturbance. I studied the direct impacts of rats on seedling communities on New Zealand islands with three different conditions regarding rats: islands where rats never invaded, islands where rats were present, and islands where rats were eradicated or where populations were low as a result of repeated eradications and reinvasions. I studied a subset of these islands to examine the indirect effects, through predation of burrowing seabirds, of invasive rats on seedlings. I also performed field, laboratory, and greenhouse experiments to determine the mechanisms driving observed patterns in seedling communities. Finally, through a literature review and laboratory trials with R. norvegicus I sought to find what plant species and plant parts invasive rats are exploiting and what characteristics may influence herbivorous consumption in rats. I found that both invasive rats and burrowing seabirds are driving factors for woody seedling communities on New Zealand islands. Woody seedling species richness and density are similar on islands with no history of rats and islands with current rat invasions. However, where rat populations have been historically high but are currently absent or low, seedling species richness is low and seedling densities are high. Low species richness on islands with a history of rats is due to selective consumption of both seeds and seedlings by rats. In addition, the presence of seabirds is associated with high species richness and density of seeds. However, at very high seabird densities, actual seedling richness and density are low due to extreme physical disturbance. Rats may prefer smaller, fleshy fruits and seeds to seedlings and other vegetative plant parts, but may be deterred from fruit or seed consumption by large size, hard seed coats, or plant chemical defenses. By understanding the separate effects of invasive rats and burrowing seabirds and the mechanisms driving these effects, island restoration efforts can be improved.
dc.subjectEcology
dc.titleThe Effects Of Invasive Rats And Burrowing Seabirds On Seed And Seedling Communities With Focus On New Zealand Islands
dc.typeThesis
dc.type.degreephd
dc.identifier.departmentDepartment of Biology and Wildlife
refterms.dateFOA2020-03-05T17:19:30Z


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