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Temporal dynamics and function of root-associated fungi during a non-native plant invasion

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Title: Temporal dynamics and function of root-associated fungi during a non-native plant invasion
Author: Day, Nicola Jean
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Antunes, Pedro M.Dunfield, Kari E.
Abstract: Net effects of root-associated fungal communities on plant growth range from positive to negative due to the combined effects of mutualists and pathogens, and are called plant-soil feedbacks. Exotic invasive plants may benefit more from associating with particular mutualists than with pathogens, resulting in overall positive feedback. Little is known about the identities and functions of root-associated fungal taxa and the time scales over which these communities may change during invasion. The overall aim of this thesis was to investigate temporal dynamics and function of root-associated fungal communities on the invasive plant, Vincetoxicum rossicum (Apocynaceae). A glasshouse study combined with molecular methods showed that V. rossicum was rapidly colonised by many mutualistic arbuscular mycorrhizal (AM) fungal taxa. However, my data suggested that it may take longer than one growing season for this species to exert major changes to the AM fungal community and associations with particular AM fungi can occur in localised areas. A second study using multiple sites representing a timeline over decades of invasion also showed no detectable pattern in total, AM, or pathogenic fungi. A plant-soil feedback study combined with high throughput sequencing showed that V. rossicum forms associations with a broad range of soil fungi that benefit plant growth. Large numbers of fungi that are pathogens on other plant species were detected in the roots but there was no evidence for stronger negative feedbacks or pathogen accumulation at sites of older invasion age. In a third study, plant pathogenicity tests with seven root-associated fungal taxa showed that these fungi had either neutral or positive effects on V. rossicum growth compared to uninoculated controls. Further testing of three of these fungi showed neutral effects on the native species Asclepias syriaca (Apocynaceae), but reduced the growth of Solidago canadensis (Asteraceae). These results suggest that in nature V. rossicum may gain a net benefit from all soil biota in its invasive range and may contribute to V. rossicum’s invasion success.
Date: 2015-01
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