Doctoral defence: Farzad Aslani “Towards revealing the biogeography of belowground diversity”

On 9 September at 10:15 Farzad Aslani will defend his doctoral thesis “Towards revealing the  biogeography of belowground diversity” for obtaining the degree of Doctor of Philosophy (in Botany and Mycology).

Supervisors:
Associate Professor Mohammad Bahram, University of Tartu
Professor Leho Tedersoo, University of Tartu

Opponent:
Professor Claus Bässler, Goethe University Frankfurt (Germany)

Summary
Belowground microbial and animal organism groups significantly regulate aboveground biodiversity and the functioning of terrestrial ecosystems. By conducting review and research studies, we examined how spatial, environmental, and plant species changes affect the belowground composition and diversity and what ecological processes underlie the community variations in association with organism functional groups. We introduced plant mycorrhizal niche space (PMNS) as a plant’s ability to exploit and shape the mycorrhizal fungal pool depending on its dependency on mycorrhizal status and plant functional traits. We provide a model to classify plant species into different PMNS, helping to predict soil mycorrhizal fungi community in a particular habitat by comparing PMNS distance between plant species. Further, we found that the Alnus species phylogeny was the primary determinant for the composition of root-associated bacterial communities, followed by edaphic, spatial and climate variables. In addition, we found Alnus species-specificity for some highly abundant bacterial phylotypes. Our analysis also showed that the importance of selection processes was higher in the community assemblage of smaller-bodied and wider niche breadth organisms. Soil pH and mean annual precipitation were the primary determinants of the community structure of eukaryotic microbes and animals, respectively. We further found contrasting latitudinal diversity patterns and strengths for soil eukaryotic microbes and animals. Taken together, this thesis shows the role of plant functional traits in structuring soil mycorrhizal communities mediating plant-to-plant competition such that there is a negative relation between the similarity of PMNS and the role of mycorrhizal fungi in plant invasion and alteration of mycorrhizal fungi following invasion. It also highlights the importance of biotic variables in shaping root-associated bacterial communities and shows that different processes underlie root-associated and soil bacterial communities on a global scale. Finally, our results point to a potential link between body size and niche breadth in soil eukaryotes and the relative effect of ecological processes and environmental factors in driving their biogeographic patterns.