# Alpha diversity

The alpha diversity or α-diversity , also called "diversity point" is a measure of the diversity of habitat. It describes the number of species that occur in a habitat or biotope . The term was introduced by the ecologist Robert Whittaker in 1960. The abundances of the individual species are irrelevant. Diversity ( english diversity ) was Germanized as diversity.

Alpha diversity can be determined by sampling . Comparisons of the alpha diversity between different samples are only permitted if the size of the samples is the same, since the number of species, and thus the diversity, usually increases with increasing sample size.

In addition to alpha diversity, Whittaker defines

• the beta diversity (β-diversity), the habitat part of the same habitat type, for the development of the number of species of different samples or. B. along an ecological gradient, characterized (species change),
• the gamma diversity (γ diversity), as a measure of the diversity on a higher spatial level, e.g. B. for an entire mountain range (suggested for a level of approx. 1 to 100 square kilometers)

In a later work Whittaker elaborated his scheme even further and introduced the terms delta and epsilon diversity. While the earlier proposals are widely recognized and used in ecology, these extensions are rarely needed.

## Statistical determination

Various methods and indices are used to determine local diversity. A common equation used to determine diversity is Shannon's :

${\ displaystyle H_ {S} = - \ sum _ {i = 1} ^ {S} \ left ({\ frac {n_ {i}} {N}} \ right) \ cdot \ ln \ left ({\ frac {n_ {i}} {N}} \ right)}$ ${\ displaystyle H_ {S}}$ : Species diversity in a biocenosis of different species${\ displaystyle S}$ ${\ displaystyle N}$ : Total number of individuals
${\ displaystyle n_ {i}}$ : Number of individuals of the -th kind${\ displaystyle i}$ ${\ displaystyle S}$ : Number of species occurring

To determine the α-diversity , Whittaker has presented the various approaches, but explains the local number of species itself as a sufficient local measure of diversity. This is the form in which alpha diversity is used within research.

## supporting documents

1. ^ Whittaker, RH (1960) Vegetation of the Siskiyou Mountains, Oregon and California. Ecological Monographs 30, 279-338.
2. Thomas M. Smith, Robert L. Smith: Ecology. Pearson Studies, Munich 2009; P. 445. ISBN 978-3-8273-7313-7 .
3. Thomas M. Smith, Robert L. Smith: Ecology. Pearson Studies, Munich 2009; P. 771. ISBN 978-3-8273-7313-7 .
4. ^ Robert J. Whittaker, Katherine J. Willis, Richard Field: Scale and species richness: towards a general, hierarchical theory of species diversity. Journal of Biogeography, 28, 453-470.
5. ^ Whittaker, RH (1977): Evolution of species diversity in land communities. Evolutionary biology 10 (editors MK Hecht, WC Steere and B. Wallace), pp. 250-268, Plenum Press (New York).