Chapter 4: Speciation and Phylogeny

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Chapter 4 Speciation and Phylogeny

• Macroevolution
• Species and Speciation
• Phylogenies Evolutionary Trees

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Biological Species

• Reproductive isolation
• Gene flow within species
• No gene flow between species
• Allopatric speciation results from
  geographic/environmental isolation
• Selection or gene drift will eventually change
  each population in different directions and
  eventually they will be incapable of
  interbreeding

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• Sympatric Speciation Niche diversification
• Different ways of making a living in the same
  place.
• Specialization toward different resource
  gathering strategies leads to different selective
  forces

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• Sympatric Speciation Niche diversification
• Different ways of making a living in the same
  place.
• Specialization toward different resource
  gathering strategies leads to different selective
  forces

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• Darwins finches
• Adaptive radiation
• Other isolation mechanisms
• Mechanical isolation
• Temporal isolation
• Behavioral isolation
• Seagulls around the World

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Phylogenies Trees of Life

• Linnaeus Linnaean System of Classification
• Based on similarity of traits
• Hierarchical
• Kingdom
• Phylum
• Class
• Order
• Family
• Genius
• Species
• Kings Play Chess On Fine Grained Sand
• Keep Pots Clean Or Family Get Sick

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Humans are
Kingdom Animal Phylum Cordates (Sub phylum
Vertebrata) Class Mammal Order Primate Family H
ominid (Super Family Hominoid) Genius Homo Species
Sapiens
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Phylogeny for the Hominoids
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Inheritance or Convergence?

• Homologous Similar because of common decent
  (share a recent common ancestor) Inheritance.
• Analogous Similar because of adaptation to the
  same or similar environmentally stable problem
  (Bird and Bat wings) - Convergence.

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Phylogenies use homologous structures (traits)
and must avoid analogous structures
Present Past
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Yes
No
No
Derived Trait Analogous Trait
Ancestral Trait (last common ancestor)
(convergence) (common ancestor
of all 3)
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Using Overall Similarity of Traits Leads to the
Wrong Family Tree
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Using Similarity of Derived Traits Leads to the
Correct Family Tree
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Using Similarity of Derived Traits Leads to the
Correct Family Tree
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Systematics the study that distinguishes
ancestral from derived traits

• Ancestral Traits
• Appear earlier in embryonic development
• Ontology recapitulates phylogeny
• Appear earlier in the fossil record
• Older traits
• Seen in out-groups
• If a trait is absence in one species but seen in
  other more distant lineages (tails)

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Genetic Distance

• DNA Hybridization

Less Related More Related
Fewer bonds More bonds
Lower Temp to break Higher Temp to break
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Molecular Clock
Neutral theory or Natural selection?
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How Good are Human Phylogenies

• Cladistic modeling of skeletal traits do not
  match the cladistic modeling of DNA distance
• Human phylogenies are based on skeletal data and
  are likely to have errors. Some argue for
  Bastian statistics approach.