Patterns in the spatial distribution of organisms provide important information about mechanisms that regulate the diversity of life and the complexity of ecosystems. Although microorganisms may comprise much of Earths biodiversity and play critical roles in biogeochemistry and ecosystem functioning, little is known about their spatial diversification. It is widely believed that the observed diversity in a microbial sample represents only a small portion of the true diversity. The problem of estimating the true number of shared microbial taxa by two sites based on sample data presents a difficult but important challenge. To more accurately quantify the similarity between two microbial communities, and thus make more reliable comparisons of micro- and macro-organism spatial biodiversity patterns, novel biostatistical techniques are needed. The proposed bioinformatics study will draw upon mark-release-recapture statistics to develop new methods for estimating the true number of shared taxa in environmental microbial samples. Using probability theory and simulation modeling, how the underlying taxa-abundance distribution in microbial communities influences the number of observed and estimated shared taxa will be quantified. These newly developed approaches will be applied to explore spatial patterns of microbial diversity in Californian vernal pool habitats.