Simpson's index is a similarity index (the higher the value the lower in diversity). If you want to use it as a diversity index you can subtract it to 1 (i.e. 1-S). Conversely, the value of the Shannon function (it is not an index) increases as diversity increases. The most used in phytoplankton ecology is probably the Shannon index because phytoplankton assemblages well fit the prerequisite of the function calculation (infinite population, sampled randomly)..

Simpson's index is more weighted on dominant species compared to Shannon index.  You can easily imagine from the equations; the latter use log in formula. It should be noted that the value can change due to the way of calculations on the basis of abundance or biomass.

What index you decide to use is to a great extent dependent on your researh question. For example, are you only interested in changes in the number of species present in a specific habitat? Or do you also want to include information on the distribution of the numbers (bundance) over the species that are present. And beware of the pitfall included in using diversity indices. An index  gives a reduction of the actual information in your samples. With respect to your question regarding temporal differences in phytoplankton a first step seems to be to inspect your data for obvious seasonal  changes in occurrence/abumdance of separate species. Study  of the proper international litterature will be very helpfull, I assume.

Kaerl Essink, retired monitoring expert Wadden Sea

Both the indices reflect  diversity. 

However, shannon is a better index as it shows both richness and abundance. To show similarity between sites we use Sorenson's index

thank you all, i guess i will go with the Shannon Wiener index since i am more interested in Evenness. i really appreciate your contributions

Those two references should improve your understanding in biodiversity if you consider Evenness.

Smith and Wilson (1996) A consumer's guide to evenness indices. Oikos

Tuomisto (2012) An updated consumer’s guide to evenness and related indices. Oikos.

Thank you.

Bar H is more reflective in nature and can predict the environmental health

Sorry for the late response, but I prefer the Simpson/Levins diversity index (used both for species diversity and diet breadth) over the Shannon-Wiener index, which is more abtruse ("physics envy") and sensitive to sample size (N). The Simpson/Levins index is better at telling you how many species or prey items are prominent, even with smaller N, because it reaches the asymptote sooner.

 -Bob Vadas, Jr.

 Can any one please tell me which index do you use in weed studies

Hi Pratibha,

It's a very interesting question. If you take the Hill's number, you can evaluate relationship between Species number, Shannon index and Simpson index. You can translate this 3 indicators as "distance", "speed" and "acceleration" in a moving context.

If you use "R" from CRAN project, i recommand you to use the "bcDiversity" command from the package entropart, who explain the difference ...

can anyone tell which index should I use in parasite infestation on freshwater snail?

The Simpson/Levins index is the best (see my publications at):

https://washingtondepartmentfishwildlife.academia.edu/RVadasJr

https://www.researchgate.net/profile/Robert_Vadas

-Bob

The 3 index specific richness, simpson and shannon were usefull, 

I prefer Shannon index as it includes more sample information, especially species richness. It's more reasonable that higher richness represents higher biodiversity.

The trouble with the Shannon-Wiener index is that it's very sample-size dependent, though less so than species richness. Hence, these indices should be cautiously, with consideration of asymptotic properties compared to N.

The Shannon-wiener index value increases with biodiversity. In contrast, the Simpson index measures the relative abundance of species, with a higher value indicating high dominance/low biodiversity. 

If you want to know the entropy of your analyzed biotope, you have to measure the ratio Simpson/Shannon ....

FYI for consideration of asymptotic-biodiversity properties compared to N:

Brooks, R.T. 2000. Annual and seasonal variation and the effects of hydroperiod on benthic macroinvertebrates of seasonal forest (“vernal”) ponds in central Massachusetts, USA. Wetlands 20: 707–715 (https://www.ncrs.fs.fed.us/pubs/jrnl/2000/ne_2000_brooks002.pdf).

-Bob

They are opposite to each other. In case of S-W index, the higher is the better but in Simpson's one the lower is the better.

No, the Simpson-Levins index is higher when there are more taxa of codominant status. So if they are 3 codominant taxa, then the index will be ~3. If there’s also 1 subdominant taxa, then the index would be ~3.5. It’s much more intuitive than the abstruse Shannon-Wiener index.

-Bob

Shannon and Sipmson Diversity indices.

Parallel use of species diversity indices in ecological studies is a general practice, and a typical case is the parallel application of the

Shannon–Wiener and Simpson index. However, while the Shannon–Wiener index is strongly influenced by species richness and by

rare species, the Simpson index gives more weight to evenness and common species. The effect of the sample size is generally

negligible for both of them.

The use of both diversity indices improves the output information of the dataset, which is unique for each community or sample

analyzed. Looking at the wider content—both emphasizing the richness, and the specimen distribution into the individual

species—adds to the more complex information of the diversity in ecosystems.

In this sense, H has an advantage over D because it depends more on species richness and less abundant species, so it is very

sensitive to even small diversity changes, and thus is widely used to assess the actual state of environment. On the other hand, D has

the advantage over H in counting more on dominant species and is not affected by less abundant elements; therefore, it is used to

show the trend of ecosystem diversity heading.

Although not published yet, I've examined sample-size vs. biodiversity effects on my own & others’ published databases for riparian & aquatic biota. Species-richness relationships were regularly significant, unless rare species were excluded from the analysis. In contrast, Simpson diversity was more rarely significant. Although I didn't test Shannon–Wiener diversity, I expect that the overall test would be more significant unless rare species were excluded. I'll have to add that analysis before publishing.

-Bob

Hello in these manuscripts you will find valuable information for your discussion. However, I suggest you review the bibliography on Jost's biodiversity indexes. it is summarized in this work: Jost, L. (2007). Partitioning diversity into independent alpha and beta components. Ecology, 88 (10), 2427-2439.

Petchey, O. L., & Gaston, K. J. (2002). Functional diversity (FD), species richness and community composition. Ecology letters, 5(3), 402-411.

Wang, R., Gamon, J. A., Schweiger, A. K., Cavender-Bares, J., Townsend, P. A., Zygielbaum, A. I., & Kothari, S. (2018). Influence of species richness, evenness, and composition on optical diversity: A simulation study. Remote Sensing of Environment, 211, 218-228.

Fontana, S., Thomas, M. K., Moldoveanu, M., Spaak, P., & Pomati, F. (2017). Individual-level trait diversity predicts phytoplankton community properties better than species richness or evenness. The ISME journal.

Cardoso, S. J., Nabout, J. C., Farjalla, V. F., Lopes, P. M., Bozelli, R. L., Huszar, V. L., & Roland, F. (2017). Environmental factors driving phytoplankton taxonomic and functional diversity in Amazonian floodplain lakes. Hydrobiologia, 802(1), 115-130.

There is a much difference between these two indexes.

One speaks about mere proportion, the other variation

Simpson Diversity

Index (SDI) was measured taking in account the number of species present as well as the relative abundance of each species. As species richness and evenness increases diversity also increases, respectively. The value of SDI ranges from 0 to 1, where

1 represent infinite diversity and 0 represent no

diversity.

So I think it is best way to analyze the whole data on single platform.

That's incorrect if you use the Simpson-diversity index (D) in Levins-breadth format (B), Sachin. Whereas the straight Simpson's eqn. is D = 1 - summation(p**2), B = 1 / summation(p**2), where p = proportional representations for each species. Pls. see my explanation above for how that intuitively works, for which the magnitude of B is indicative of the # of dominant & subdominant spp.

@ Robert L. Vadas, I do agree at some point, if we use statics, then you will find at sometime, it do not matches with the ground ecology assemblages. So we have to very careful while using statics.

Statistical analysis is the basis of good science. Strong beliefs are the domain of politics & religion:

Vadas, R.L. Jr. 1994. The anatomy of an ecological controversy: honey bee searching behavior. Oikos 69: 158-166 (http://beesource.com/point-of-view/adrian-wenner/the-anatomy-of-an-ecological-controversy-honey-bee-searching-behavior).

-Bob

HI,Sama,

The shannon wiener index and Simpson indices include the measurement of community heterogeneity.

Shannon wiener index bapplied information theory. The main measuring object of information theory is the content of system order or disorder. Shannon wiener index (Shannon-Weiner index) is used to describe the disorder and uncertainty of individual species. The higher the uncertainty, the higher the diversity. There are two factors in Shannon-Weiner diversity index: (1) number of species, i.e. richness; (2) the average or evenness of individual distribution in the species. A large number of species can increase diversity. Similarly, increasing the uniformity of individual distribution among species will also increase diversity. If each individual belongs to a different species, the diversity index is the largest. If each individual belongs to the same species, its diversity index is the smallest.

Simpson diversity index D= probability that two individuals randomly sampled belong to different species, i.e. D=1- probability that two randomly sampled individuals belong to the same species,namely D=1- the sum of the number of species per species divided by the square of the total number. It can be seen that the more species in the community, the more uniform the distribution of various individuals, and the higher the index, indicating a good diversity of the community. The greater the Simpson index, the higher the diversity. It is a scalar of α-diversity. Rare species play a smaller role in simpson's diversity index, while common species play a larger role. The species diversity estimated by this method needs more samples.