Integrating Above and Belowground Components of Biodiversity across Spatial Scales: The Role of Host Plants in the Distribution of Arbuscular Mycorrhizal Fungi

The Arbuscular Mycorrhizal (AM) fungi are a group of obligate plant root endosymbionts, which form associations with an estimated two thirds of terrestrial plant species. Their extra-radical mycelium extends throughout the soil and absorbs nutrients that are transferred to their host plant in exchange for a purely phytogenic carbon supply. Due to their ubiquity and their functional importance, they are the subject of much research into their community ecology, yet much is still unknown. For instance: whether or not AM fungi display preference for certain host plant species; how environmental heterogeneity and energy availability affect communities; and the relative influence of niche and neutral processes. This thesis describes experiments which profile AM fungal communities and environmental properties of their habitat at different spatial scales in different plant species. Network analysis revealed patterns indicative of niche-based processes structuring AM fungal communities more than neutral processes, phenotypic trade-offs between AM fungi, and of priority effects influencing diversity and unevenness. Difference between plant species in the heterogeneity of surrounding soil was dependent on spatial scale. The effect of decreased carbon allocation on AM fungal communities is greater in more heterogeneous habitats. These results suggest that the detection of host plant preference in AM fungi is dependent on spatial scale of sampling, driven by interspecific variation in plant root architecture, soil physical properties and AM fungal vital rates.