Measuring Diversity

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Measuring Diversity
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Community A
Community B
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Species diversity

• Often defined as a combination of the number of
  species and their relative abundance.

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Diversity Divisions

• Alpha diversity refers to species richness
• Beta diversity describes the degree of change in
  species richness from one habitat to another.
• Gamma diversity relates to the total regional
  species diversity that results from the number of
  habitats present.

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Diversity Divisions

• Alpha diversity refers to species richness
• Beta diversity describes the degree of change in
  species richness from one habitat to another
  habitat patchiness
• Gamma diversity relates to the total regional
  species diversity that results from the number of
  habitats present.

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Diversity Divisions

• Alpha diversity refers to species richness
• Beta diversity describes the degree of change in
  species richness from one habitat to another.
• Gamma diversity relates to the total regional
  species diversity that results from the number of
  habitats present.

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Number of species

• Species richness
• Method simply count the number of different
  species you observe, regardless of abundance.
• Therefore, if a species occurs 1 or 100 times,
  its richness is still 1.

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Community A
Community B
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Relative Abundance

• Species evenness assesses the relative
  numerical importance of each species
• the contribution of each species to the total
  number of individuals in the community

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Relative Abundance

• Method count up the number of each individual
  observed or collected and divide by the total
  number observed or collected.
• RA n/N
• the percent contribution made by each species to
  the community

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Community A
Community B
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Simpson Index

• A measurement that accounts for the richness and
  percent of each species from a biodiversity
  sample within a community.

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Simpson Index

• This index assumes that the proportion of
  individuals in an area indicates their importance
  to diversity.
• So, it measures not only diversity but dominance
  as well.

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Simpson Index

• Can actually refer to any one of 3 closely
  related indices.
• Simpson's Index (D) measures the probability that
  two individuals randomly selected from a sample
  will belong to the same species
• Ranges between 0 and 1, the lower the value, the
  greater the sample diversity

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Simpson Index

• Simpson's Index of Diversity 1 D measures the
  probability that two individuals randomly
  selected from a sample will belong to the same
  species
• Ranges between 0 and 1, the greater the value,
  the greater the sample diversity

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Simpson Index

• Simpson's Reciprocal Index 1 / D provides the
  number of equally common categories (e.g.,
  species) that will produce the observed Simpson's
  index.
• Ranges between 0 and total species collected,
  the higher the value, the greater the diversity

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D 0.3 (Simpson's Index)
OR Simpson's Index of Diversity 1 - D
0.7 Simpson's Reciprocal Index 1 / D  3.3
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Simpson Index

• Simpson's Index gives more weight to the more
  abundant species in a sample. The addition of
  rare species to a sample causes only small
  changes in the value of D

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Shannon-Wiener index

• Also been called the Shannon index and the
  Shannon-Weaver index.
• Used to compare diversity, doesnt give a measure
  of dominance.
• Similar to Simpson's Index, this measure takes
  into account species richness and proportion of
  each species within a community.

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H' -S piln(pi)
where H Information content of sample, Index of
species diversity, or Degree of Uncertainty, s
Number of species pi Proportion of total sample
belonging to ith species IN EXCEL LN (pi)
will give you the natural log
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Shannon-Wiener index

• Unlike the Simpson index, H is interpreted that
  the higher the score the more diverse.

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What does diversity tell us?

• Comparison purposes
• Recovery purposes
• Community interaction
• Community summary