Gamma Taxonomy: Describing Intraspecific Variation

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Gamma TaxonomyDescribing Intraspecific Variation

• BIOL 100
• 15 September 2009

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Subspecies

• Geographic portion of a species
• Unique genetic traits
• Intergrades often exist at margins of subspecies
  contact
• Formation of subspecies
• Isolation for a period of time (allowing
  differentiation)
• Re-contact and genetic mixing (intergradation)

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Subspecies taxonomy

• Trinomial nomenclature
• Genus species subspecies
• Always one nominate subspecies
• Subspecific epithet specific epithet
• Found within subspecies containing holotype of
  the species
• Intergrades two subspecific epithets separated
  by ?

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Fig 17.5 p.352
Melospiza melodia subspecies (4 of 34)
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Painted turtle (Chrysemys picta) subspecies
Chrysemys picta marginata
Chrysemys picta bellii
Chrysemys picta picta
Chrysemys picta dorsalis
Note Type specimen of C. picta was collected
in1783 in Lancaster Co., PA
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Painted turtle (Chrysemys picta) intergrades
Chrysemys picta bellii ? marginata
Chrysemys picta picta ? marginata
Chrysemys picta bellii ? dorsalis
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Smooth softshell subspecies
Midland smooth softshell, Apalone mutica mutica
(red) Gulf Coast smooth softshell, Apalone
mutica calvata (blue) (No known intergrades)
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Phylogeography

• Genetic study of population differentiation
  within a single species
• Produces phylogenetic tree of populations
• Used to test validity of subspecies designations
  or discover hidden intraspecific differences

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Bleakneys (1958) Hypothesis

• Subspecies of C. picta arose during isolation
  brought on by most recent Ice Age glaciers,
  12,000 years ago
• C. p. picta in southeast
• C. p. dorsalis in Lower Mississippi River basin
• C. p. bellii in southwest
• marginata arose via post-glacial contact of C.
  p. bellii and C. p. dorsalis
• Later met C. p. picta in New England

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HANDOUTStarkey et al. 2003Chrysemys picta
phylogeography
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HANDOUTWeisrock and Janzen 2000Apalone mutica
phylogeography