Ch' 6: Evolutionary ProcessesOutcomes

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Ch. 6 Evolutionary Processes/Outcomes
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Species

• Some species are good indicators of environmental
  conditions
• Ex, Quercus laevis (turkey oak). Found in dry
  sandy soils (sandhills) of the SE coastal plain

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Species

• Other species have very broad environmental
  ranges
• And often vary in form in different types of
  habitats
• Are these differences due to genetic traits (are
  they adaptations?) or due to phenotypic
  plasticity?

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Ecotypes

• Recall
• Adaptation genetically based trait with
  survival/reproductive value
• Phenotypic plasticity environmentally induced
  differences (adjust individual to local
  conditions)
• Phenotype Genotype current environment
• How evaluate?

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Ecotypes

• Phenotype Genotype current environment
• How evaluate?
• Common garden experiment collect members of
  species from range of environments and plant in
  same environment

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Ecotypes

• Common garden experiments
• 1920s Turesson (Sweden)
• Examined many widespread European species
• Ex, hawkweed (Hieracium)

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Ecotypes

• 1920s Turesson (Sweden)
• Described ecotypes as
• based on genetically determined traits
• traits discrete, unique
• populations interfertile (same biological
  species)
• locally adapted populations (traits with survival
  value)

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Ecotypes

• Common garden experiments
• 1920s Clausen, Keck, Hiesey (California)
• Also studied widespread species
• Used elevation gradient

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Ecotypes

• 1920s Clausen, Keck, Hiesey (California)
• Ex, Potentilla glandulosa
• Found several ecotypes
• Named some as subspecies

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Ecotypes

• So, many widespread plant species form ecotypes
• But some form ecophenes populations whose
  differences disappear in common garden
• Example, pygmy forest of Mendocino, CA

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Ecotypes

• What happens when seeds of pygmy trees planted on
  normal soil?

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Ecotypes

• So, many widespread plant species form ecotypes
• But detailed experiments showed ecotypes
  intergrade

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Ecotypes

• Traits form a cline (continuous variation)
• Along range of habitats, form ecocline continous
  variation in traits along environmental gradient

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Ecotypes

• Ecotypic traits
• Morphology stature, leaf traits, floral traits,
  etc.
• Phenology timing of life cycle events (flowering
  timing, bud break, germination timing)
• Physiology germination cues, photosynthesis
  rates, etc.

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Ecotypes

• Ex. of eco-physiological ecotypes alpine sorrel
  (Oxyria digyna). Found in arctic (high latitude)
  and alpine (high altitude) tundra

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Ecotypes

• Examples
• Agrostis tenuis (bentgrass) in England
• Pasture grass
• Found in areas of old Roman-era metal mines

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Ecotypes

• Examples
• Plants on mine spoil were metal tolerant
• Those on normal soil were metal intolerant
• Ecotypes were as close as 1 m from one another!
• Metal tolerance determined by single allele

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Ecotypes

• Examples
• Delphinium (larkspur) in Colorado mountain
  meadows
• Seeds planted next to parent plant and next to
  another plant 50 m away
• Seedlings grew better in native neighborhood
• May show local adaptation to soil/competing plants

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Ecotypes

• But, ecotypes not always found where expected
• Example, foothill pine (Pinus sabiniana) on
  normal vs. serpentine soils

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Ecotypes

• Serpentine rock with chemical imbalances (lots
  Mg, Ni, Cr but little Ca)
• Soil has low N, P. High Cr, Ni. Low Ca/Mg ratio.
• Soil relatively rocky, dry, infertile

Serpentine barrens
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Ecotypes

• Many serpentine areas have foothill pine
• Ecotype on serpentine?

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Ecotypes

• No. Seedlings from serpentine and normal soils
  BOTH grew poorly on serpentine soil and well on
  normal soil.
• Foothill pine is tolerant of serpentine conditions

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Acclimation

• Plastic, temporary change in organism caused by
  past environment
• Phenotype genotype current env. past env.
• Ex, Senecio vulgaris (groundsel)
• Weedy annual plant

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Acclimation

• Ex, Senecio vulgaris (groundsel)
• Seeds germinated at different temperatures, then
  transferred into same environment and grown 80
  days.

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Acclimation

• Ex, Cold hardening process by which plant
  prepares for winter temperatures
• Often, solute accumulation (freezing point
  depression), allow water to leak into spaces
  between cell walls (reduce turgor)

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Ecotypes Practical applications

• Useful for revegetation/reforestation
• Need to plant proper ecotype in particular area

Revegetating mine spoil
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Ecotypes Practical applications

• Ex, shortleaf pine (Pinus echinata)
• Native to SE U.S.

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Ecotypes Practical applications

• 5 seed zones areas from which seeds should be
  obtained for local plantings.

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Ecotypes Practical applications

• Sometimes can get complicated
• Ex, douglas fir in Oregon

22 foot diameter old growth!
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Ecotypes Practical applications

• Sometimes can get complicated
• Ex, douglas fir in Oregon

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Ecotypes Practical applications

• Often seed zone info not available for native
  species
• Solution collect seeds locally!