Microorganisms comprise much of Earth's biodiversity and play critical roles in biogeochemical cycling and ecosystem functioning, yet little is known about their spatial distribution. It has historically been assumed that due to their unique biology, free-living microorganisms are globally ubiquitous and cosmopolitan, and thus have fundamentally different biodiversity scaling relationships relative to those observed for other forms of life. Although these differences have been assumed to be universally characteristic of microorganisms, the empirical evidence for this is scant, and recent observations are revealing microbial biodiversity scaling relationships that are qualitatively similar to those of plants and animals. This research builds on these recent studies to provide a more comprehensive understanding of the spatial scaling of microbial biodiversity. This project will use beta-diversity analyses as a theoretical tool to answer questions about the relative importance of dispersal history and environmental heterogeneity in controlling the spatial scaling of microbial diversity. Analyses will be based on a spatially-explicit set of microbial diversity data, generated by a sampling scheme that is of global scale, and focused on soils in the Mediterranean-climate regions of California, Chile, South Africa, and Australia. Microbial diversity will be assayed using molecular methods focused on methane oxidizing bacteria. Statistical analyses will determine the relative importance of the processes generating and maintaining microbial beta diversity, and how these processes vary with region, spatial scale and taxonomic resolution. This work will contribute broadly to a general understanding of global biodiversity patterns. An outreach component of this project will engage students in the local Merced school district in a program that promotes the application of math to the environmental science.
