Matos Franco, Giovana, authorOde, Paul, advisorPearse, Ian, committee memberSmith, Melinda, committee memberTrivedi, Pankaj, committee member2024-05-272024-05-272024https://hdl.handle.net/10217/238521Russian knapweed (Rhaponticum repens) is an invasive noxious weed present in the United States and two insect biocontrol agents have been released to assist with its management: the gall midge (Jaapiella ivannikovi) and the gall wasp (Aulacidea acroptilonica). Since their establishment, no concrete impacts of biocontrol agents onto Russian knapweed have been measured, neither their impacts on interactions between Russian knapweed and local microbiomes. To address this knowledge gap, observational and manipulative studies were conducted to investigate the effects of biocontrol agents on Russian knapweed fitness as well as its associated microbiomes. We found that Russian knapweed associates with a core microbiome that can assist with invasion in the introduced range as well as, in root samples collected from sites where gall wasp were present, lower microbiome diversity was observed, indicating potential negative effects on overall plant health. In garden conditions, water availability positively correlated with plant growth, negatively correlated with insect establishment, and shaped microbiomes in root associated tissues. Results of this dissertation highlights how introduction of biocontrol agents shifts pre-established relationships between invasive plants and microbiomes as well as how such relationships could be impacting the success of biocontrol programs.born digitaldoctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.gallsbiocontrolmicrobiomeText