5 elements of evolutionary theory

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5 elements of evolutionary theory

• Lineages change over time
• Different species can be linked to common
  ancestors (branching)
• Changes are gradual and accumulate over long
  periods of time
• Change occurs at the population level, expressed
  as proportions of individuals
• Natural selection leads to adaptation without
  teleology

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Descent with Modification

• Tools for Testing Hypotheses about Derivation

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Darwins hypothetical tree
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• Recently created volcanic islands Daphne Major
  Minor, Galapagos

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Critical observations

• Intergradation of form localized distribution
• Examples of Galápagos mockingbirds
• and Galápagos finches
• Confirmation of Lyells conclusion of geological
  age

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Subdivision of species without islandsSampling
locations of lynx Nature 425 69-72 (Sept., 2003)
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Distribution of mt Haplotypes for lynx in Canada
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Evidence for Descent with Modification

• Direct Observation
• Herbivorous insects
• HIV
• PRRS arterivirus

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Evidence for Descent, cont

• Experiments with artificial selection

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Evidence for Descent, cont

• Homology
• molecular (genetic code, aa sequences)
• structural (bone structures in vertebrates)
• Vestigial organs (the
• imperfection of nature)

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Evidence for Descent, cont

• Fossil Record
• transitional forms
• clustering of species in form

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Phylogenetic Analysis I
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Phylogenetic Analysis Questions

• What are the methods used to reconstruct
  evolutionary history?
• What characteristics can be used to infer common
  ancestry?
• How does one construct hypotheses about
  phylogenetic trees?
• How does one test hypotheses about phylogenetic
  trees?

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How do we reconstruct the history of speciation?

• Traditional systematics
• Placement of species into taxonomic system
• Interpretation of conservative characters
• Emphasis on phenotypic similarity
• Cladistics (Willi Hennig)
• Identify branching that leads to monophyletic
  groups (evolutionary information included)
• Based on shared, derived characters

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Important jargon

• Parsimony
• Synapomorphy
• shared derived character
• Homoplasy shared but not derived
• Convergence (similarity from similar selection,
  but different common ancestors)
• Reversals (DNA sequence similarity often based on
  mutation then back-mutation)

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Homoplasy exemplified Eastern Glass Lizard
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Create a nested hierarchy (phylogenetic tree)
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Alternative hypotheses for derivations
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A phylogenetic tree based on synapomorphic
characters
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Principles of cladistics

• Hennigs Auxiliary Principle.Never assume
  convergence, parallel evolution, or reversal
  always assume homology in the absence of contrary
  evidence (parsimony).
• Grouping Rule.Synapomorphies are evidence for
  common ancestry relationships, whereas
  convergences, and parallelisms are useless in
  providing evidence of common ancestry (Hennig,
  1966).

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Classification using just one character (fin)
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A more parsimonious classification