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Executive Summary

The year 2009 marked both the 200th anniversary of Darwin’s birth and the 150th anniversary of the publication of his landmark book, On the Origin of Species. In August 2009, to celebrate these milestones, the American Academy of Microbiology convened a colloquium in the Galapagos Islands, where Darwin made some of his most crucial observations, to consider a new question: what would Darwin have made of the microbial world? The ability to sail to remote sites like the Galapagos, and access to specimens collected by himself and other avid naturalists, gave Darwin the information he needed to develop a conceptual framework for understanding life’s visible diversity. Today, new discoveries and technical capabilities in microbiology are providing information that for the first time makes it possible to develop a conceptual framework for deepening our understanding of the diversity of the microbial world.

Darwin focused his attention on visible life forms, which actually make up only a small fraction of the living world—the invisible world of microorganisms was as yet largely unexplored in his time. Yet Darwin’s theory has proven remarkably robust; despite some fundamental differences between microorganisms and the rest of the living world, the two lynchpins of Darwin’s theory—descent with modification and natural selection—have proven as powerful in explaining microbial evolution as they have in explaining macrobial evolution. Since Darwin, the advent of Mendelian Genetics and the Modern Synthesis have provided a wealth of new tools to evolutionists; these tools are also of fundamental importance in the modern study of microbiology.

The scientists gathered at the colloquium considered two fundamental questions:

■ Is the balance of evolutionary mechanisms, for example natural selection or drift, or individual and group selection, consistent among microbes and similar between microbes and macrobes?

■ How are the mode and tempo of microbial evolution influenced by Earth’s diversity of environments, and the changing global environment, and how are microbes themselves driving these changes ?

The colloquium provided an opportunity for individuals with expertise in evolutionary biology, genetic engineering, mycology, virology, microbial ecology, and other fields to discuss these issues and review the areas in which research is needed to fill gaps in our understanding.