Are niche width correlated with abundance in the blackcap and other island animals

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Are niche width correlated with abundance? (in
the blackcap and other island animals)
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Niche width

• Definition the proportion of some n-dimensional
  resource space used by a species of a community
  (Van Valen 1965)
• Niche width consists of two components.
• The within-phenotype component
• The between-phenotype component

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Islands
6. Are niche width correlated with abundance?

• Low species density
• Low interspecific competition
• Increase in population size abundance increase
• Extreme phenotypes harvest unexploited resources
• Extreme phenotypes or extreme plasticity are
  selected for - increase in intra-populational
  variation
• Niche width increase

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Data base of islands and birds
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Assumption 1 Low species density
Mainland?
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• Common species generally have wider niches than
  less common ones
• Niche measurements can be morphological variables
• Relationship between common (abundance) and niche
  width (morphological variables)?

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Niche variation model

• (Van Valen 1965)
• A positive relation between niche width and
  morphological (phenotypical) variability??
• Difficulties testing the model
• Sample bias (Willson 1969)

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Abundance and niche width measured as CV of bill
length
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• Abundance and CV of bird bill length are
  significantly correlated (Rothstein 1973618) (15
  passerines, Tres Marías Isles)
• Conclusion
• Common species generally have wider niches than
  less common ones

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High abundance on islands
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High abundance - wide nichesexamples Mauritian
animals
D. Hansen
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(No Transcript)
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High species density Complex, weak stabilizing
selection regime
Low species density Density compensation Simple,
strong directional selection regime
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No. Species on islands

• Database

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Assumption 1 Low species density
What determines the number of species on islands?
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• The number of species on an island is a dynamic
  balance between immigration and extinction

MacArthur Wilson 1967 The theory of island
biogeography
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The theory of habitat saturation

• The most important determinant of island species
  number is habitat diversity
• David Lack 1976