Comparing the Shannon-Wiener Index with Other Biodiversity Measures

 

Compare Shannon, Simpson Index, and margalef richness image by BING  

*Heri Tarmizi

However, comparing it with other indices, such as the Simpson Index, the Margalef Richness Index, and the Berger-Parker Dominance Index, reveals different aspects of biodiversity

The Shannon-Wiener Index (H') is one of several indices used to measure biodiversity in ecological studies. Each index has its strengths and limitations, and understanding how they compare can provide a more comprehensive picture of biodiversity. This essay will compare the Shannon-Wiener Index with other commonly used indices, such as the Simpson Index, the Margalef Richness Index, and the Berger-Parker Dominance Index.

The Shannon-Wiener Index (H')

The Shannon-Wiener Index is derived from information theory and measures the uncertainty in predicting the species of a randomly selected individual from a community. The formula for the Shannon-Wiener Index (H') is:

where $S$is the total number of species (species richness), and $p_i$ is the proportion of individuals belonging to the $i$-th species.

The Simpson Index (D)

The Simpson Index measures the probability that two individuals randomly selected from a sample will belong to the same species. It is more sensitive to the dominance of a few species in a community. The formula for the Simpson Index (D) is:

$D={\sum }_{i=1}^S{p}_i^2$

Where  $S$ is the total number of species, and $p_{\mathrm{i }}$is the proportion of individuals belonging to the $i$-th species. The value of D ranges from 0 to 1, with lower values indicating higher diversity. An alternative form, the Simpson Diversity Index (1 - D), ranges from 0 to (1 - 1/S), providing a direct measure of diversity.

Comparison with Shannon-Wiener Index

• Sensitivity to Dominance: The Simpson Index is more influenced by the dominance of particular species than the Shannon-Wiener Index, making it more sensitive to changes in the abundance of dominant species.
• Interpretation: The Shannon-Wiener Index gives more weight to rare species, while the Simpson Index emphasizes the importance of common species.
• Scale: Both indices scale differently, with the Simpson Index being bounded between 0 and 1, whereas the Shannon-Wiener Index can theoretically range higher.

The Margalef Richness Index (R)

The Margalef Richness Index is a simple measure of species richness, adjusted for sample size. It is calculated using the formula:

$R=\frac{S-1}{\ln (N)<span\; style="text-align:\; justify;"></span>}$

where  $S$ is the total number of species, and $N$ is the total number of individuals in the sample.

Comparison with Shannon-Wiener Index

• Focus on Richness: The Margalef Index focuses solely on species richness and does not account for evenness, unlike the Shannon-Wiener Index, which considers both richness and evenness.
• Sample Size Adjustment: The Margalef Index adjusts for sample size, making it useful for comparing samples of different sizes, whereas the Shannon-Wiener Index can be affected by sample size.
• Simplicity: The Margalef Index is simpler to calculate and interpret, focusing purely on the number of species present.

The Berger-Parker Dominance Index (d)

The Berger-Parker Dominance Index measures the proportion of the most abundant species relative to the total number of individuals. It is given by:

$d=\frac{N_{max}}{\mathrm{N<span\; style="text-align:\; justify;"></span>}}$

where  $N_{max}$ is the number of individuals in the most abundant species, and $N$

$N$ is the total number of individuals.Comparison with Shannon-Wiener Index

• Focus on Dominance: The Berger-Parker Index focuses on the dominance of the most abundant species, providing a measure of the relative abundance of the dominant species. In contrast, the Shannon-Wiener Index provides a more balanced view of diversity, considering both common and rare species.
• Sensitivity: The Berger-Parker Index is highly sensitive to the presence of a dominant species, making it useful for detecting changes in dominance patterns.
• Interpretation: The Shannon-Wiener Index is more informative for communities with many species of relatively equal abundance, while the Berger-Parker Index highlights dominance.

Practical Applications and Case Studies

Forest Ecosystems

In a study of bird diversity in forest ecosystems, researchers compared the Shannon-Wiener Index and the Simpson Index to evaluate the impact of logging on avian communities. They found that both indices showed a decrease in diversity in logged areas, but the Simpson Index was more sensitive to the dominance of a few species that thrived in disturbed habitats (Bregman et al., 2014).

Urban Ecosystems

Urban ecologists applied the Shannon-Wiener Index and the Margalef Richness Index to assess biodiversity in city parks. While the Margalef Index highlighted the richness of species in parks with diverse plantings, the Shannon-Wiener Index provided insights into the evenness of species distributions, revealing that some parks, despite having many species, were dominated by a few (Aronson et al., 2017).

Agricultural Landscapes

In agricultural landscapes, the Berger-Parker Index was used alongside the Shannon-Wiener Index to monitor the impact of different farming practices on bird communities. The Berger-Parker Index highlighted the dominance of a few species in intensively farmed areas, while the Shannon-Wiener Index showed greater overall diversity in organic farms with more balanced species distributions (Hole et al., 2005).

Conclusion

The Shannon-Wiener Index is a valuable tool for measuring biodiversity, integrating species richness and evenness into a single value. However, comparing it with other indices, such as the Simpson Index, the Margalef Richness Index, and the Berger-Parker Dominance Index, reveals different aspects of biodiversity. Each index has its strengths and is suited to specific research questions and ecological contexts. By using multiple indices, ecologists can gain a more comprehensive understanding of biodiversity patterns and the factors influencing them.

References

• Bregman, T. P., Sekercioglu, C. H., & Tobias, J. A. (2014). Global patterns and predictors of bird species responses to forest fragmentation: implications for ecosystem function and conservation. Biological Conservation, 169, 372-383.
• Aronson, M. F., Lepczyk, C. A., Evans, K. L., Goddard, M. A., Lerman, S. B., MacIvor, J. S., ... & Vargo, T. (2017). Biodiversity in the city: key challenges for urban green space management. Frontiers in Ecology and the Environment, 15(4), 189-196.
• Hole, D. G., Perkins, A. J., Wilson, J. D., Alexander, I. H., Grice, P. V., & Evans, A. D. (2005). Does organic farming benefit biodiversity? Biological Conservation, 122(1), 113-130