Monday, September 27, 2010, 12:00PM - 1:00PM
Bacteria control major nutrient cycles and directly influence plant, animal, and human health. However, we know relatively little about the forces shaping their large-scale ecological ranges. I will discuss a meta-analysis of patterns in the distribution of individual bacterial taxa at multiple levels of phylogenetic resolution within and between Earth’s major habitat types. This analysis suggests that while macro-scale habitats structure bacterial distribution to some degree, most bacteria are confined to single assemblages. In addition, the most cosmopolitan taxa are also the most abundant in individual assemblages. One possible explanation for these patterns is that bacteria are subject to dispersal limitations. Thus, I will also discuss an experiment designed to test the age-old “everything is everywhere but the environment selects” hypothesis. Patterns of bacterial community succession were examined in jars containing heterotrophic media separated by either short (~1m) or long (>1 km) distances, where environmental factors including shading, temperature and precipitation were held constant. Initial beta diversity (i.e., the difference between communities) was low but it increased over time as communities shifted from those dominated by Bacillus to more diverse, move even communities. Geography affected the distribution of rare taxa but not abundant organisms. Together, these results support similarities between the biogeography of macroorganisms and microbes and suggest that bacteria may also experience dispersal limitations that are related to their local abundance.