MIGRATION: Development

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MIGRATION Development Evolution

• WFSC 422 Ethology
• Presentation 3.3

Dr. Jane M. Packard, WFSC TAMU j-packard_at_tamu.edu
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Worldwide migrations
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Geological Changes

• Continental drift- e.g. gonwandaland
• http//www.scotese.com/sfsanim.htm
• Glacial expansion and retreat
• http//www.scotese.com/paleocli.htm
• Uplift of mountains- e.g. rockies
• http//www.scotese.com/pangeanim.htm

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Migration Process of Adaptation

• Development in individuals
• Is a sense of direction inherited?
• Is the ability to learn landmarks inherited
  (stars or landscape)?
• Evolution of species
• continental drift
• glacial expansion retreat

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Example Migratory Eels

• Development- juveniles
• Instinct in juveniles- American genotype
  navigates to a different current than European
  genotype
• Development- adults
• Stages of maturity- physiological changes related
  to reproduction are dependent on size not age
  (effect of environment)

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Example Eels (continued)

• Evolution- juveniles adults
• Ancestors reproduced and grew in Sargasso sea
  before the continents drifted apart
• Derived- travel long distance to rivers
• Divergence of American European stocks
  (genotypes)

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Logic of Natural Selection- eel migration

• V ( C) if there was variation in the ancestral
  population of eels, such that some drifted with
  ocean currents and some did not before the
  continents separated
• H (D) if the tendency to move into the ocean
  currents was heritable
• D (F) if those that moved into and drifted with
  the ocean currents were more likely to grow to
  reproductive age because they found better food
  in the rivers compared to those genotypes that
  stayed in the Sargasso Sea
• P (E) then the genotypes for juvenile migration
  would have persisted in the population even as
  the continents drifted apart and the rivers got
  further and further away from the Sargasso Sea

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DEVELOPMENT Monarch butterfly migration

• Mature monarchs that overwinter fly north and
  reproduce on the closest milkweed
• Monarchs hatched in the summer migrate north and
  lay eggs (like a relay race following the green
  plants north)
• Monarchs that emerge in the fall do not mature
  and migrate south
• Ability to switch directions depending on
  environmental conditions is heritable

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EVOLUTION Monarchs (continued)

• Ancestral species was a tropical butterfly that
  moved uphill during the dry season and downhill
  during the wet season
• When the glaciers receded, the distribution of
  milkweed moved further north new species evolved
  that were adapted to northern climates
• Monarchs diverged from the tropical ancestors,
  still not tolerating cold latitudes or dry
  summers, but migrating with the seasonal
  greenbelt

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Logic of Natural Selection- monarch migration

• V ( C) if there was variation in the ancestral
  population such that some genotypes only moved up
  and down the mountains, and other genotypes
  followed the seasonal greenbelt in latitude
• H (D) if the variation was heritable
• D (F) if the genotypes that moved with the
  seasonal greenbelt were more successful at
  reproducing as the glaciers receded
• P (E) then the genotypes for staying in the
  mountains would have decreased and the genotypes
  for migrating with the seasonal greenbelt would
  have increased, resulting in the migratory
  adaptation seen in the modern species

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SUMMARY

• DEVELOPMENT think in terms of what is
  instinctive/learned and how this changes with age
  or conditions
• EVOLUTION think about how continents diverged,
  and glaciers moved
• Examples eel and monarch migration

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Action Items

• Answer Q3.5 3.6
• Search for key authors Brower, L or Urquhart,
  FA
• Post to WebCT discussion