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713 Lecture 1. Microbial biogeography and diversity. “Everything is everywhere, the environment selects”. Everything is everywhere?. Pros. Cons. Pros High dispersal rate (?) Extremely fine partitioning of the environment Extreme abundance ??

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713 lecture 1

713 Lecture 1

Microbial biogeography and diversity




Pros and cons bacterial ubiquity

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


How do you test for cosmopolitanism or endemism
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?



Why differences between continents and islands
Why differences between continents and islands?

  • http://en.wikipedia.org/wiki/Island_biogeography

  • In your words?

  • What about microbes?


Calculating ta curves
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?


So almost everything is everywhere low z values

So almost everything is everywhere (low z values)

What about in more extreme environments?


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