Alpha diversity

This MedLibrary.org supplementary page on Alpha diversity is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:

Related Sponsors

BM Pharmacy Generic pharmaceuticals at unbeatable prices. Insomnia, men's health, hair health, pain control. bmpharmacy.com
Online Pharmacy Carisoprodol, tadalafil, sildenafil, vardenafil and more... xlpharmacy.com
MedBasket.com Discreet. Inexpensive. Fast shipping. Great selection. What more can we say? medbasket.com
Frugalmed 2000 reasons to shop with us first. frugalmed.com
Ads by Tiva

Alpha diversity (α-diversity) is the biodiversity within a particular area, community or ecosystem, and is usually expressed as the Species richness of the area. This can be measured by counting the number of taxa (distinct groups of organisms) within the ecosystem (eg. families, genera, species). However, such estimates of species richness are strongly influenced by sample size, so a number of statistical techniques can be used to correct for sample size to get comparable values.

Contents

Simpson's Diversity Index

D=\frac{\sum_{i=1}^S n_i(n_i-1)}{N(N-1)}

Where S is the number of species, N is the total percentage cover or total number of organisms and n is the percentage cover of a species or number of organisms of a species.


Shannon index

H^\prime = -\sum_{i=1}^S p_i \ln p_i

where

   * ni The number of individuals in each species; the abundance of each species.
   * S The number of species. Also called species richness.
   * N The total number of all individuals
   * pi The relative abundance of each species, calculated as the proportion of individuals of a given species 
     to the total number of individuals in the community: n_i\over N

Fisher's Alpha

Rarefaction

Rarefaction takes hypothetical subsamples of n organisms from the more-sampled region, and calculates the average number of species in such subsamples. This average can be compared to the number of species actually found in the less-sampled region

Other measures of diversity

Alternative ways to measure biodiversity include[1].:


  • Beta diversity – species diversity between ecosystems; this involves comparing the number of taxa that are unique to each of the ecosystems.
  • Gamma diversity – taxonomic diversity of a region with several ecosystems.
  • Phylogenetic diversity – or 'Omega diversity'. The differences or diversity between taxa
  • Global diversity – overall biodiversity of Earth.

Diversity may not be congruent at all taxonomic levels and diversity patterns may vary depending on the type of diversity measured, as seen in the example to the left.

See also

External links

An explanation of many specific biodiversity terms using illustrations http://www.uwsp.edu/geo/faculty/heywood/geog358/Diversity/Biodiversity.htm

References

  1. ^ Whittaker, R.H., 1972. Evolution and measurement of species diversity. Taxon 21: 213–251.

Wikipedia content modification information:

  • This page was last modified on 20 July 2008, at 17:54.

Wikipedia Authorship and Review

Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.

Wikipedia Usage Guidelines

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Alpha diversity".

The URL for this specific entry is:

All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.