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Species Abundance and Diversity (1).docx

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McMaster University
Kim Dej

November 5 , 2012 Biology 2F03: Fundamental and Applied Ecology Species Abundance and Diversity (1) Species abundance and diversity - species differ in their abundance; some are rare; few are very abundant; most are moderately abundant - diversity: a combination of the number of species and their abundance - species diversity is higher in complex environments or in environments with modest (intermediate) level of recurring disturbance Question - Is there any order to the commonness and rarity of species: some are rare some are common, Lognormal distribution - take a community of species living together, count their individuals:  plot number of individuals with number of species  few species are rare  few species are very common  most species have intermediate density (6-30 here)  this is a general pattern wherever one studies communities  depends on sample size Community metrics - richness – the number of species, S - evenness – the degree of equality among abundances, E - example: two communities with equal number of individuals and species Rank abundance curves - abundance rank vs population abundance - abundance rank: decreasing in abundance of species - community A is much more uneven than community B - community A might be dominated by one species because conditions are better for that species - to compare such situations diversity indices are used - ∑ , where:    p is the proportion of an i species Rank abundance: examples - habitats and taxa differ in the number of species and equitability of their abundances - question: which factors cause such differences? Question - do common causes of this pattern exist and can be identified? Spatial complexity - field observations (warblers in Maine) - the number of warbler species and their overall abundance increase with increasing vegetation stature - 2-4 species in short vegetation - 4-5 species and a greater total number of individuals - height of vegetation indicates greater 3D complexity - a survey of a number of forests produced this picture - bird diversity (measured by H’) is greater in forests with greater foliage height diversity - does a planted forest offer the same opportunity for birds Spatial complexity - height of vegetation indicates greater 3D complexity - a survey of a number of forests produced this pic
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