A field study of specificity in the arbuscular mycorrhizal symbiosis

Host specificity in the arbuscular mycorrhizal (AM) symbiosis has been difficult to assess in the field. Here I report on a study designed to determine whether different plant species associate with unique communities of arbuscular mycorrhizal fungi (AMF), and how increasing plant diversity affects the composition of AMF communities. We sampled soil from a long-term common garden study – the biodiversity field experiment at the Cedar Creek Ecological Research Centre in Minnesota, USA. The soil samples were taken from plots with varying plant diversity (0, 1, 4, and 16 species) and AMF DNA was extracted from these samples for 454 sequencing to assess fungal community composition, host specificity, and plant diversity effects in the AM symbiosis. Results indicate that there is evidence for functional specificity in the AM symbiosis, particularly with grasses, which show distinct AMF communities from other plant functional groups, such as legumes and non-legume forbs. Due to loss of samples in the sequencing pipeline, little evidence could be garnered for host specificity at the plant species level. Though this study provides some evidence for host specificity at the functional group level, the results indicate that relative abundance of AMF taxa is affected by plant functional group, therefore also supporting the idea that AMF are more generalist in nature. Similarly, when investigating the impact of plant diversity on AMF community composition and phylogenetic composition, this study shows that that plant diversity has an effect on AMF community composition, but not on AMF species richness. Overall, the results of this study indicate that the maintenance of AMF community composition is affected by plant type and diversity above ground, and that other factors may be responsible for regulating the diversity of AMF communities in the soil. However, this study does provide a better understanding of belowground/aboveground interactions and community scale dynamics in the AM symbiosis.Arts and Sciences, Irving K. Barber School of (Okanagan)Biology, Department of (Okanagan)Graduat