Applications of Species Diversity Indices

There are many kinds of species diversity indices and all have their advantages and disadvantages. One of the advantages of the Shannon-Wiener index is that it is not greatly affected by sample size. One of the early studies to look at the effects of sample size was one by Wilhm and Dorris. They calculated species diversity indices from values that were pooled from successful samples. They found that sample size had a very small effect on the measures of species diversity.

One of the advantages of using diversity indices such as the Shannon-Wiener index is that they capture a lot of information in one expression. This can be helpful when communicating large sets of data to a general audience. On the other hand such expressions can appear to be very impressive only because they are derived from simple mathematics. It is essential therefore that anyone using such an index explains how it is calculated.

However, the measures of species diversity must be put into context. The context can usefully be considered in two parts. One is the minimum and maximum that is theoretically possible and the second is the range of values that could be expected in one particular ecological community. It is easy to measure the minimum and maximum for any species diversity index. Similarly, it is relatively easy to assess the likely limits in any ecological community.

Species diversity indices are widely used in ecological monitoring and state of the environment reporting. Although species diversity indices do summarize a lot of data, it is recommended that in ecological monitoring, diversity indices are used alongside other measures of the state of the environment. This is simply because different measures of the state of the environment are based on different parameters or variables.

Diversity in ecology has been the subject of much research. There have been debates about links or otherwise between diversity and resilience of ecosystems. In 1983, for example, Moore provided a brief summary of several research programs on ecological diversity and stress. In that summary, he refers to several authors including del Moral, who reported some research on subalpine meadows on the slopes of the Olympic Mountains in the western United States. In these grasslands, productivity is related to many biotic and abiotic factors. It was found that diversity (measured by the Shannon-Wiener index) had maximum values where there was moderate stress and where total productivity was suboptimal. Furthermore, it was reported that species transplanted from high-diversity sites to highly productive sites generally survived well if the surrounding plots were cleared on competitors. However, they did not do well if the plots were not cleared.

In another study (summarized by Moore), the researchers Hixon and Brostoff described complex links where predatory damsel fish in Hawaiian coral reefs control populations of herbivorous fish which in turn influence the algae components of the reef ecosystem. They found that the greatest diversity (Shannon-Weiner index) was found inside the damselfish territories and the lowest outside.

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