What limits/influences distributions?

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What limits/influences distributions?

• 1) Historical Factors
• factors associated with past events or distance
  (in geologic time) contingency and priority
  effects
• 2) Contemporary Factors
• factors operating in ecological time (e.g.
  behavioral, abiotic and biotic factors) that
  limit or affect patterns of distribution

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1) Historical Factors

• Evidence that geologic history plays a role in
  distributions
• Continental drift Marsupial, ratite and
  Nothofagus distribution (vicariance explanation -
  fragmentation of environ ie. splitting of a
  tectonic plate) in contrast to dispersal limits
• Glaciation Temperate forest tree distributions
• Area spatially inaccessible non-native species
  (e.g. starlings, cane toads, large mammals on
  islands, etc)
• Insufficient time (relative to dispersal speed)

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• How can we determine if historical or
  contemporary factors have affected distributions?

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Examine fossil record and consider continental
drift Godwana in Permian (286-245 mya). See also
Fig. 4.7 in Krebs
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Outside of range
Do manipulative/transplant experiments
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2) Contemporary factors

• A. Habitat selection Why are some habitats
  occupied? Individuals choose based on stimuli
  from
• Landscape, terrain
• Type of nesting or feeding sites
• Density of resources /or conspecifics
• Life stage, size of individual
• Cultural based on early experiences
• Evoln reasons ultimate reason(s)
• Ecological reasons proximate

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best
worst
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2) Contemporary factors

• A) Habitat selection individuals choose based
  on stimuli from
• Landscape, terrain
• Type of nesting or feeding sites
• Density of resources /or conspecifics (aphids)
• Life stage, size of individual
• Cultural based on early experiences
• Evoln reasons ultimate reason(s)
• Ecological reasons proximate

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2) Contemporary factors

• B. Biotic factors
• Limitation by competition
• Limitation by predation
• Allelopathy
• Mutualism

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2) Contemporary factors

• C. Abiotic factors means and extremes
• Leibigs rule of the minimum
• Shelfords law of tolerance
• Acclimation

Fig. 3.3
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How do organisms expand ranges?Modes of
dispersal

• Diffusion - gradual spread
• Jump- movement across long distance
• Colonization rates are driven not by the mean
  dispersal rates, but by extreme dispersal events
  (Krebs 2001).
• Secular - spread in conjunction with adaptation

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Zebra mussel dispersal
Sometimes all three operate together
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