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2. There are over 1000 technical papers on the topic.

3. Biological diversity is shortened as biodiversity. Whether it means plants, animals, communities, genes or all of these must be determined from use and the context.

4. Diversity may mean:

1. Richness
2. Variance (statistical)
3. Abundance
4. Evenness
5. Equitability
6. Relative rarity (as in Shannon-Weiner index)

1. Taxa
2. Areas
3. Time
4. Treatment
5. Baseline-to-...
6. Behavior
7. Trophic groups
8. Sex
9. Age
10. Weight
11. Area (layers, size, shape, number of units)
12. Similarity
13. Genetic

7. Richness, R, means the number of taxa. This area has 30; that one has 40. The one with 40 is more rich, more diverse, with greater biodiversity.

8. When a species becomes extinct, the area has a loss in richness. "Preserve species" is a richness slogan, only one aspect of diversity.

9. Taxonomic "lumpers" reduce richness; "splitters" increase richness.

10. Genetics allows "splitting" of taxa or organisms to the individual; demes are analyzable; color phases (as in grouse or screech owls or squirrels) may also display diversity; subspecies (as in birds) may be appropriate analytical categories. There is no standard or criterion for judgement.

11. Abundance and richness are combined in the Simpson index.

V₁ = Summation all i's p_i²

The proportion of animals or plants in each ith species is used. Also called a dominance index, the value is 1.0 when all are in one species. This does not sound very diverse so the modified Simpson is usually used, namely

V₂ = 1.0 - V₁

12. The Shannon-Weiner index is frequently used. It is:

V₃= H = - Summation all products( p_ilog p_i)

Note the negative sign that is related to the logarithm of a proportion being negative, thus V₃ finally being positive.

The proportions are used as above. Log_e, log₁₀, and log₂ are all used. There is no best value; the more evenly distributed, the larger will be the value of V₃; several sets of proportions can give the same value of V₃. V₃ is a value in search of a meaning. It is called "average rarity."

13. Equitability, V₄, is a statistic comparing V₃ to the maximum value that would be obtained if all individuals in the sample studied were evenly distributed among the observed species present. It is relative Shannon-Weiner diversity.

14. V₂ and V₄ seem managerially useful.

15. Evenness, has an index

V₅ = V₃ / log R

It is another expression of evenness, as is V₃.

16. I think the ranked abundance of species in a natural system will usually approach the negative exponential or "reversed J" distribution, abundant to rare. How well an observed distribution fits this hypothesized distribution may be worth studying. The lack of evenness may be of much more interest than its presence.

17. There are many published ways to produce an index to biodiversity. In preliminary studies, a loss of one species can cause half these indices to increase, half to decrease. Arguing for biodiversity can be a useful political position because of this either/or as well as both/and condition.

18. The manager should pick a system performance measure, say "species X observations per hour along a transect", then develop a multiple regression, each independent variable being other species, values of each being abundance. Keep the abundance information separately so that effect of change in one can be observed on species.

19. Equifinality is a real problem if indices are used. Very different inputs from very different systems, when computed, can result in the same number, e.g., the "biodiversity". Avoid indices; work with regression analyses.

This Web site is maintained by R. H. Giles, Jr.
Last revision January 17, 2000.