Ecological and evolutionary invasion dynamics of Lonicera maackii (Amur honeysuckle) in relation to white oak savanna restoration management at Nachusa Grasslands, Illinois, USA
McCarragher, Shannon R.
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This interdisciplinary research explores the ecological impacts and underlying evolutionary mechanisms associated with the spread of Lonicera maackii (Amur honeysuckle), one of the most aggressive and abundant invasive species throughout the Midwest United States. The main goal of this research is to better understand how the encroachment of Amur honeysuckle impacts the Midwest native Quercus alba (white oak) population in a Nature Conservancy oak savanna restoration project (Nachusa Grasslands) located in Lee County, Illinois, USA, with particular focus on mechanisms required for successful oak regeneration and recruitment (i.e. carbon assimilation, soil quality, soil moisture/ temperature, and plant available nutrients). This study also aims to explore the spatial-temporal long distance dispersal patterns of Amur honeysuckle, as inferred by population genetics, in order to better understand the mechanisms and pathways by which Amur honeysuckle is spreading throughout Illinois.;Ultimately, the low light levels measured in the understory of the oak savanna restoration study site at Nachusa Grasslands yielded marginal seasonal carbon assimilation totals for white oak seedlings, especially when compared to the high seasonal carbon assimilation totals modeled for white oak seedlings had they been growing in full sun light conditions. In relation to belowground properties, this study found no significant differences between any of the soil characteristics (i.e. wet macro-aggregate soil stability, moisture, temperature, carbon nitrogen ratios, and nutrient levels) measured in adjacent soil samples collected under and away from Amur honeysuckle within the oak savanna restoration study site at Nachusa Grasslands. Findings from the population genetics analyses in this research supports previous research that Amur honeysuckle displays characteristics associated with stratified dispersal. Specifically, a lack of correlation between genetic distance and geographic distance for the Illinois Amur honeysuckle subpopulations suggest that active gene flow between these subpopulations occurs via regional long distance dispersal events. The New York Botanical Garden subpopulation was identified as genetically isolated from all other subpopulations. The Arnold Arboretum at Harvard University and The Morton Arboretum also displayed patterns of genetic isolation from the other subpopulations, more so than from each other. Management recommendations, based off findings from this research, are provided.