AbstractsBiology & Animal Science

Rules of acquisition: small-scale field studies on arbuscular mycorrhizal fungal and plant communities

by Sebastian Horn

Institution: Freie Universität Berlin
Department: FB Biologie, Chemie, Pharmazie
Degree: PhD
Year: 2015
Record ID: 1107982
Full text PDF: http://edocs.fu-berlin.de/diss/receive/FUDISS_thesis_000000099308


The study of assembly of plants and microbial communities is an important subject of ecological research as it aids our understanding of species diversity and hence ecosystem functions. Mycorrhizal fungi are of particular importance due to their role as prime symbionts for most land plants. The community composition of plants and mycorrhizal fungi are governed by environmental, spatial and biotic patterns, whose individual contributions are an active field of research and ongoing debate. Since the processes are tightly interwoven, greenhouse experiments offer limited access to the actual processes which take place in nature. In the present dissertation, the community assembly rules of plants, AMF and the interplay between the two organism groups were studied in a high diversity ecosystem in the "Oderhänge Mallnow", offering a large diversity of plants and steep gradients in soil environmental properties on a small scale. Two field samplings were conducted, one studying a single macroplot of 15x15m and analyzing the AM fungi community composition of the focal plant on the study site, Festuca brevipila roots and surrounding soil. The second sampling was conducted 6 months later, using three macroplots of 15x15m, 12x12m and 12x12m, and focused on AMF communities in root and soil of Festuca brevipila plus the composition of the surrounding plant communities. In Chapter II, the plant community assembly patterns were studied. It was found that important roles of environmental factors that prevail at larger scales also are present at smaller scales. Additionally, biotic interactions causing species segregation and effects of the spatially structured environment share a significant influence in plant community composition. In Chapter III, the AM fungal communities from the first sampling and their respective assembly patterns were analyzed. Results indicate that environmental influences are negligible for AMF, but rather spatial and phylogenetic patterns dominate the assembly of communities. Phylogenetic clustering was observed not only in the dominant but also in the rare species, indicating that trait conservatism and resulting selection principles are a main route for AMF community assembly. Apart from this, dispersal limitation and stochastic position events contribute to the composition of an AMF community at a given spot, as evident due to the low mobility of AM fungi in the soil. These patterns may be related to direct or indirect positive interactions among fungi and their biotic environment. In Chapter IV, the interactions of AMF and plant communities from the second sampling were analyzed in context of the Passenger and Driver framework. AMF follow their strong spatial structure and phylogenetic sorting patterns, albeit strong phylogenetic clustering could not be observed in this particular sampling, indicating potential seasonal influences. They only have insignificant influence on either their surrounding plant community composition or their phylogenetic distribution, hence rejecting the Driver hypothesis.…