Alpha diversity
In
Scale considerations
Both the area or
Different concepts
Ecologists have used several slightly different definitions of alpha diversity. Whittaker himself used the term both for the species diversity in a single subunit and for the mean species diversity in a collection of subunits.[1][2] It has been argued that defining alpha diversity as a mean across all relevant subunits is preferable, because it agrees better with Whittaker's idea that total species diversity consists of alpha and beta components.[7]
Definitions of alpha diversity can also differ in what they assume
Calculation
Suppose species diversity is equated with the effective number of species, and alpha diversity with the mean species diversity per subunit. Then alpha diversity can be calculated in two different ways that give the same result. The first approach is to calculate a weighted generalized mean of the within-subunit species proportional abundances, and then take the inverse of this mean. The second approach is to calculate the species diversity for each subunit separately, and then take a weighted generalized mean of these.[4][13]
If the first approach is used, the equation is:
In the equation, N is the total number of subunits and S is the total number of species (species richness) in the dataset. The proportional abundance of the ith species in the jth subunit is . These proportional abundances are weighted by the proportion of data that each subunit contributes to the dataset, , where is the total number of individuals in the dataset, and is the total number of individuals in subunit j. The denominator hence equals mean proportional
If the second approach is used, the equation is:
This also equals a weighted generalized mean but with exponent 1 - q. Here the mean is taken of the qDαj values, each of which represents the effective species density (species diversity per subunit) in one subunit j. The nominal weight of the jth subunit is , which equals the proportion of data that the subunit contributes to the dataset.
Large values of q lead to smaller alpha diversity than small values of q, because increasing q increases the effective weight given to those species with the highest proportional abundance and to those subunits with the lowest species diversity.[4][13]
Examples
Alpha diversity can be calculated in both extinct and extant landscapes.
Examples of extinct alpha diversity studies
- The survival of amphibians and reptiles communities through the Permian-Triassic Extinction[14]
- The reorganization of Ordovician benthic marine communities[15]
Examples of extant alpha diversity studies
- High tree diversity in throughout the Amazon Rainforests of Ecuador[16]
See also
- Beta diversity
- Dark diversity
- Diversity index
- Gamma diversity
- Zeta diversity
- Global biodiversity
- Measurement of biodiversity
- Phylogenetic diversity
References
- ^ doi:10.2307/1943563
- ^ doi:10.2307/1218190
- ^
- ^ Colwell, R. K. and Coddington, J. A. (1994) Estimating terrestrial biodiversity through extrapolation. Philosophical Transactions: Biological Sciences, 345, 101-118.
- ^ a b Tuomisto, H. (2011) Commentary: do we have a consistent terminology for species diversity? Yes, if we choose to use it. Oecologia, 167, 903-911.
- ^ Lande, R. (1996) Statistics and partitioning of species diversity, and similarity among multiple communities. Oikos, 76, 5-13.
- ^ Veech, J. A. et al. (2002) The additive partitioning of species diversity: recent revival of an old idea. Oikos, 99, 3-9.
- ^ Hill, M. O. (1973) Diversity and evenness: a unifying notation and its consequences. Ecology, 54, 427–432
- ^ Jost, L. (2006) Entropy and diversity. Oikos, 113, 363–375
- ^ Jost, L. (2007) Partitioning diversity into independent alpha and beta components. Ecology, 88, 2427–2439.
- ^
- PMID 18198148.
- ^ Westrop, S. R.; Adrain, J. M. (2010). "Trilobite alpha diversity and the reorganization of Ordovician benthic marine communities".
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