Evolution of Sympatric Color Polymorphism in the California Clingfish, Gobiesox rhessodon

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Evolution of Sympatric Color Polymorphism in the
California Clingfish, Gobiesox rhessodon

• Rosemary Byrne

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Intro to G. rhessodon

• San Bartolome Bay, Baja California to Pismo
  Beach, California
• 3 sympatric color morphs (orange, brown, gray)
• Small size, simple diet could make them good lab
  animals

Pismo
San Bartolome Bay
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Nest guarding
Lifecycle
Adult Life in the Intertidal to 11 m.
Pectoral suction cup
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Questions

• Are the 3 color morphs really all one species?
  If yes, can any genetic divergence be detected?
• What forces are sustaining the 3 forms?

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Project Outline

• Sequencing - look for cryptic species or signs of
  speciation through sequence divergence
• Laboratory Crosses - do we see hybrid breakdown
  or epistasis?
• Mate Choice Experiments - assortative mating
  present?

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Sequencing

• Sequence fast evolving mt. locus, like CR, from
  many individuals of brown, gray, and orange
  morphs
• Analyze using program like Sequencher
• Measure sequence divergence

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Lab Crosses

• Mate gray-gray, brown-brown, orange-orange for F1
  generation
• Cross gray-brown, orange-brown, etc. for F1
  generation
• Compare different crosses for both phenotype,
  survivorship, and viability

If viability differences are seen, we could study
the genes involved in speciation process.
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Mate Choice
Control for fish size and observe, count mating
behaviors towards each color female
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Adjust for female preference
Assortative mating present?
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Summary

• Sequence data will show us whether or not 3 color
  morphs have diverged
• Lab crosses will show us if hybrid breakdown or
  decreased survivorship exists (could provide new
  model to study process of genetic divergence)
• Mate choice experiments can show us whether
  assortative mating seems to play a role (this can
  result in sympatric speciation)

These all investigate in-house forces
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Alternative Explanations

• 1. Negative frequency-dependent selection,
  where rare types have higher survival rates
• 2. Search image formation in predators

These are both predator-induced alternatives and
are difficult to quantify.
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References

• Allen, L. G. (1983) Larval development of the
  northern clingfish, Gobiesox-maeandricus.
  Copeia. 2, 551-554.
• Briggs, J. C. (1955) A monograph of the
  clingfishes. Stanford Ichthyology Bulletin. 6,
  1-224.
• Punzalan, D., et al. (2005) Perceptual processes
  and the maintenance of polymorphism through
  frequency-dependent predation. Evolutionary
  Ecology. 19, 303-320.
• Seehausen, O., et al. (1999) Color Polymorphism
  and sex ratio distortion in a cichlid fish as an
  incipient stage in sympatric speciation by sexual
  selection. Ecology Letters. 2, 367-378.