Beta diversity
In ecology, beta diversity (β-diversity or true beta diversity) is the ratio between regional and local species diversity. The term was introduced by R. H. Whittaker[1] together with the terms alpha diversity (α-diversity) and gamma diversity (γ-diversity). The idea was that the total species diversity in a landscape (γ) is determined by two different things: the mean species diversity at the local level (α) and the differentiation among local sites (β). Other formulations for beta diversity include "absolute species turnover", "Whittaker's species turnover" and "proportional species turnover".[citation needed]
Whittaker proposed several ways of quantifying differentiation, and subsequent generations of ecologists have invented more. As a result, there are now many defined types of beta diversity.[2][3] Some use beta diversity to refer to any of several indices related to compositional heterogeneity.[4][5][6] Confusion is avoided by using distinct names for other formulations.[2][3][7][8][9][10]
Beta diversity as a measure of species turnover overemphasizes the role of rare species as the difference in
Types
Whittaker beta diversity
Gamma diversity and alpha diversity can be calculated directly from species inventory data.[2][13] The simplest of Whittaker's original definitions of beta diversity is
β = γ/α
Here gamma diversity is the total species diversity of a landscape and alpha diversity is the mean species diversity per site. Because the limits among local sites and landscapes are diffuse and to some degree subjective, it has been proposed that gamma diversity can be quantified for any inventory dataset and that alpha and beta diversity can be quantified whenever the dataset is divided into subunits. Then gamma diversity is the total species diversity in the dataset and alpha diversity the mean species diversity per subunit. Beta diversity quantifies how many subunits there would be if the total species diversity of the dataset and the mean species diversity per subunit remained the same, but the subunits shared no species.[2][7]
Absolute species turnover
Some researchers have preferred to partition gamma diversity into additive rather than multiplicative components.[14][15] Then the beta component of diversity becomes
βA = γ - α
This quantifies how much more species diversity the entire dataset contains than an average subunit within the dataset. This can also be interpreted as the total amount of species turnover among the subunits in the dataset.[2]
When there are two subunits, and presence-absence data are used, this can be calculated with the following equation:
where, S1= the total number of species recorded in the first community, S2= the total number of species recorded in the second community, and c= the number of species common to both communities.
Whittaker's species turnover
If absolute species turnover is divided by alpha diversity, a measure is obtained that quantifies how many times the
βW = (γ - α)/α = γ/α - 1
When there are two subunits, and presence-absence data are used, this equals the one-complement of the
Proportional species turnover
If absolute species turnover is divided by gamma diversity, a measure is obtained that quantifies what proportion of the species diversity in the dataset is not contained in an average subunit.[2] It is calculated as
βP = (γ - α)/γ = 1 - α/γ
When there are two subunits, and presence-absence data are used, this measure as ranged to the interval [0, 1] equals the one-complement of the Jaccard similarity index.[2]
β-diversity patterns
Although understanding the change in
Diversity partitioning in the geologic past
Major diversification events in the geologic past were associated with shifts in the relative contributions of alpha- and beta-diversity (diversity partitioning). Examples include the
See also
- Alpha diversity
- Biotic homogenization
- Bray–Curtis dissimilarity
- Dark diversity
- Diversity index
- Gamma diversity
- Global biodiversity
- Jaccard distance
- Measurement of biodiversity
- Zeta diversity
References
- JSTOR 1943563.
- ^ .
- ^ .
- .
- PMID 21070562.
- S2CID 6244637.
- ^
- S2CID 24562429.
- S2CID 8917573.
- S2CID 19271108.
- ISSN 1466-8238.
- S2CID 24693167.
- PMID 20980309.
- JSTOR 3545743.
- .
- ISBN 978-0-520-26868-5. Retrieved 28 June 2011.
- JSTOR 1218190.
- ^ Sørensen TA (1948). "A method of establishing groups of equal amplitude in plant sociology based on similarity of species content, and its application to analyses of the vegetation on Danish commons". Kongelige Danske Videnskabernes Selskabs Biologiske Skrifter. 5: 1–34.
- ^ PMID 30839691.
- S2CID 86777476.
- .
- S2CID 206535334.
- .
- hdl:10072/57312.
- S2CID 38892245.
- hdl:10044/1/32808.
- PMID 25825755.
- S2CID 2826581.
- S2CID 132194066.
- S2CID 85880638.
- S2CID 86225708.