Rapid Evolution in Moths

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Rapid Evolution in Moths

• Saltational Shifts in Pheromone Systems

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Moth Mating Behavior

• Male moths use specialized, species-specific
  blends to fly upwind and locate a mate.
• Optomotor anemotaxis process
• Antagonist compounds in the blends of other
  species

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Pheromone Production

• Biosynthesis of pheromone components usually
  begins with unsaturated fatty acid derivatives
• Changes made sequentially to produce end-point
  volatiles
• Sometimes multiple pathways can result in the
  same chemical end-point

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Pheromone Systems

• Canalization of response logically prevents small
  changes from accruing over time.
• How, then, do pheromone systems evolve?
• Saltational shifts instant changes in female
  blend or male response due to mutation.

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Reproductive isolation add water and stir

• Mutant females can arise in a population.
• Genes for female pheromone production and male
  tracking are not linked.
• Allows male mutations to track new blends to
  evolve independently from pheromone production in
  their female counterparts.

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Saltational Shifts

• Pheromone blends usually consist of two-three
  components.
• High stabilizing selection. Why?
• How likely is it that small changes could build
  up?

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Hidden Genes

• Many moths possess multiple enzymes for pheromone
  production only some of these produce actual
  reaction products.
• Many pseudogenes and mRNA that is never
  transcribed lurk in pheromone glands.

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The Birth and Death of a Gene (not the life story
of Gene Hackman)

• Sudden activation of certain genes through a
  promoter change, etc. can create new components
  in a pheromone blend
• Subsequent inactivation of other genes could
  eliminate ancestral components from the blend

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Mutations Drive Evolution

• Turning genes on and off can have profound
  impacts upon the ultimate phenotype of the
  organism.
• Males with broadly tuned ORNs or new types of
  receptors are prepared to track any new mutations
  in the female population

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ECB vs. ACB(this isnt sports, folks)

• Ostrinia species nubilalis and furnacalis
• Pheromones (Z) and (E)-11-tetradecenyl acetate
  (nubilalis) (Z) and (E)-12-tetradecenyl acetate
  (furnacalis)
• Rare males within the ECB population

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ECB vs. ACB

• Desaturase genes/gene products clearly play a
  role in the recent speciation
• Broader theme within the Lepidoptera?
• Contrast this to the situation in roaches.
• Evolutionary themes by Order?

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Other Examples

• Trichoplusia ni mutant females and male
  selective breeding to create a response
• Y. rorellus unique pheromone blend compared to
  others of its genus (tetradecenyl acetate)
• Also, this moth has neurons sensitive to the
  sympatric species pheromones

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Questions

• Does this rapid form of evolution, i.e.
  saltational shifts in pheromone systems, really
  qualify as rapid evolution as our group has
  defined it? Argue your case

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Questions

• Can single mutations arise and persist long
  enough to cause an insipient new species? Would
  this be influenced by rapidly expanding
  populations as we have previously discussed?

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Questions

• Mating disruption is a common facet of a good IPM
  program. This technique involves flooding a
  field with the pheromone of a pest species (via
  dispensers) such that their natural ability to
  find mates is lowered or negated, reducing the
  reproduction of a population. How do you think
  this information about rapid evolution might
  affect a good IPM decision (if at all)?

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Questions

• Does gene multifunctionality and subsequent
  diversification play a significant role in the
  ancestry of gene families? Would this
  diversification speed up or slow down the rate of
  evolution of new species?

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Questions

• Does linkage between olfactory receptor neuron
  genes and the genes for pheromone production
  (e.g. desaturases) need to occur in order to
  promote rapid speciation, or would it inhibit
  speciation?

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References

• Wendell L. Roelofs and Alejandro P. Rooney.
  Molecular genetics and evolution of pheromone
  biosynthesis in Lepidoptera. Proc. Natl. Acad.
  Sci. 100 9179-9184.
• Wendell L. Roelofs et al. Evolution of moth sex
  pheromones via ancestral genes. Proc. Natl.
  Acad. Sci. 99 13621-13626.
• Thomas C. Baker. Mechanism for saltational shifts
  in pheromone communication systems. Proc. Natl.
  Acad. Sci. 99 13368-13370.