Adaptive radiation

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Adaptive radiation

• The rapid diversification of a lineage
• The factors that drive adaptive radiation
• key innovations/mutations/novelty
• ecological opportunity

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Examples of adaptive radiation

• Group Key innovation(s)

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The Cambrian explosion

• The fossil record
• Ediacaran fauna
• Burgess shale
• 540-500 Mya
• The molecular evidence
• Hemoglobin clock
• Ecological underpinnings
• Increased atmospheric oxygen
• Predator-prey coevolution
• Global warming and rising sea levels following
  the most extensive glaciations in history

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What does the molecular clock say about the
timing of the Cambrian explosion?

• Bruce Runnegar (1982) 900Mya
• Wray et al. (1996) 1000-1200Mya
• How can these molecular data be reconciled with
  the fossil data?
• What observations or experiments would shed light
  on the cause of the discrepancy?

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The (pre?) Cambrian explosion

• 1200Mya

from Rasmussen et al. (2002) Science
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What are these?
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Phylogeny
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Adaptation
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Tarweed huggers

• Larry Gerry Carr (U Hawaii)
• Moe Robert Robichaux (U AZ)
• Curly Bruce Baldwin (UC Berkeley)
• http//www.botany.hawaii.edu/faculty/carr/silversw
  ord.htm

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Adaptive radiation in real time

• Paul Rainey and Mike Travisano (1998) Nature 394
  69-72.
• Adaptive radiation in bacteria (Pseudomonas)
  grown in liquid culture (microcosm)
• Why use bacteria for evolutionary experiments?

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Adaptive radiation in real time

• Two environments
• Homogeneous (shaken, not stirred)
• Heterogeneous (unshaken)
• Replicate experiments founded with a clonal
  isolate of the smooth morph
• Plated onto solid agar media at daily intervals
  to measure frequency of morphotypes

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Pseudomonas
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Pseudomonas
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Pseudomonas
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Pseudomonas