The groups took advantage of existing distance-decay formulas: mathematical formulas previously developed for plant and animal communities that describe how many more types, or species, can be expected to be shared from two samples taken far apart say at opposite ends of a field or a lake than from two samples taken close together.
The researchers were the first to couple this ecological thinking with information about microbes found using molecular tools developed in just the last 10 years, Horner-Devine says. Because it is so difficult to determine exact species of microorganisms, the researchers looked for DNA, or pieces of DNA, and compared that to tell different "types" apart.
It's a different taxonomic resolution than species, Green says, but it is a consistent measure of community composition. Green and her co-authors sampled the microbial fungi Ascomycota in desert soils of a 62-square-mile national park in Australia. The Horner-Devine paper was based on bacteria sampled across a half-acre in a New England salt marsh.
The studies span different microbial taxa, habitats, continents, molecular techniques and spatial scales, leading Green to say, "Our data firmly establishes that like plants and animals, microbes are not randomly distributed but rather exhibit spatially predictable, aggregated patterns at multiple spatial scales."
This result has big implications, says Hughes. "If the composition of bacteria is different in different places, then they might be performing the
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Contact: Sandra Hines
shines@u.washington.edu
206-543-2580
University of Washington
8-Dec-2004