Difference between revisions of "Measurements of biodiversity"
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A variety of objective measures have been created in order to empirically measure biodiversity. The basic idea of a diversity index is to obtain a quantitative estimate of biological variability that can be used to compare biological entities, composed of direct components, in space or in time. | A variety of objective measures have been created in order to empirically measure biodiversity. The basic idea of a diversity index is to obtain a quantitative estimate of biological variability that can be used to compare biological entities, composed of direct components, in space or in time. | ||
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| + | Three sorts of indices can be distincted: | ||
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| + | '''1. Species richness indices''': Species richness is a measure for the total number of the species in a community but in practice is the actual number of the species in the community usually immeasurable. | ||
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| + | '''2. Evenness indices:''' Evenness expresses how evenly the individuals in a community are distributed over the different species. | ||
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| + | '''3. Taxonomic indices:''' These indices look after the taxonomic relation between different organisms in a community, for example the mean taxonomic distance between two organisms. Taxonomic diversity can be visualized by the distance to connect two organisms along the branches of a phylogenetic tree. | ||
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| + | These indices can be used on different spatial scales: | ||
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| + | * Alpha diversity refers to diversity within a particular area, community or ecosystem, and is measured by counting the number of taxa within the ecosystem (usually species) | ||
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| + | * Beta diversity is species diversity between ecosystems; this involves comparing the number of taxa that are unique to each of the ecosystems. | ||
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| + | * Gamma diversity is a measure of the overall diversity for different ecosystems within a region. | ||
Revision as of 13:25, 21 August 2007
A variety of objective measures have been created in order to empirically measure biodiversity. The basic idea of a diversity index is to obtain a quantitative estimate of biological variability that can be used to compare biological entities, composed of direct components, in space or in time.
Three sorts of indices can be distincted:
1. Species richness indices: Species richness is a measure for the total number of the species in a community but in practice is the actual number of the species in the community usually immeasurable.
2. Evenness indices: Evenness expresses how evenly the individuals in a community are distributed over the different species.
3. Taxonomic indices: These indices look after the taxonomic relation between different organisms in a community, for example the mean taxonomic distance between two organisms. Taxonomic diversity can be visualized by the distance to connect two organisms along the branches of a phylogenetic tree.
These indices can be used on different spatial scales:
- Alpha diversity refers to diversity within a particular area, community or ecosystem, and is measured by counting the number of taxa within the ecosystem (usually species)
- Beta diversity is species diversity between ecosystems; this involves comparing the number of taxa that are unique to each of the ecosystems.
- Gamma diversity is a measure of the overall diversity for different ecosystems within a region.
