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Bacterial Ubiquity: Pros and Cons of Microbial Biogeography

Explore the concept of "Everything is everywhere" in microbial diversity, discussing high dispersal rates, environmental partitioning, and challenges like species identity blurring. Learn methods for testing cosmopolitanism and endemism, including sampling, distance-decay relationships, and taxa-area relationships. Understand how microbial diversity varies between continents and islands, and consider the impact of classification methods on diversity calculations. Discover the complexities of microbial biogeography in extreme environments.

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Bacterial Ubiquity: Pros and Cons of Microbial Biogeography

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Presentation Transcript

  1. 713 Lecture 1 Microbial biogeography and diversity

  2. “Everything is everywhere, the environment selects”

  3. Everything is everywhere? Pros Cons

  4. Pros High dispersal rate (?) Extremely fine partitioning of the environment Extreme abundance ?? Extreme resistance to variable conditions; dormancy, spores Side effect: ease of study because they’re everywhere Blurring of species identity by HGT/LGT (horizontal gene transfer) Cons Not all environments can be alike (e.g. temperature, pH, pressure, elevation) Past measurements of diversity too coarse Dispersal not as efficient as once thought There is a difference between short-term presence and persistence following dispersal Limited previous knowledge of species diversity Inadequacy of prior methods (culture-dependent) Pros and cons, bacterial ubiquity

  5. How do you test for cosmopolitanism or endemism? • Sampling – does sample absence = true absence? (what is your null model?) • Distance-decay relationship • Does community similarity change with geographic distance? • Taxa-area relationship • Does total diversity change with area, and at what rate?

  6. Taxa-area relationships

  7. Why differences between continents and islands? • http://en.wikipedia.org/wiki/Island_biogeography • In your words? • What about microbes?

  8. Calculating TA curves • No generalizations possible, but a power-law relationship can be assumed, i.e. • S = Az • 0.1 < z < 0.3, in general, but steeper for islands (.25 < z < .35). Why? • What is z like for microorganisms? • How does classification method affect z?

  9. So almost everything is everywhere (low z values) What about in more extreme environments?

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