Dear,
Normally the Shannon-Weaver index and Simpson index are correlated.
However, in my study on the diversity of 2 bacterial communities following results were obtained.
Shannon-Weaver index:
X: 2.72
Y: 2.83
Inverse Simpson index:
X: 5.50
Y: 8.14
My question is if these results are plausible, or should I not trust them?
Kind regards
Probably it is due to the scale difference of the two indexes. Given species number n, the theoretical maximum of the Shannon-Wiener index is log(n). While the inverse Simpson index ranges from 1 to +∞ regardless of species number, and the slope increases with the inverse Simpson index. Thus, I think comparing the absolute values of them is meaningless.
To check this problem, please transform the two indexes into the same scale (e.g. both ranging from 0 and 1), or calculate indexes from more samples to see the correlation of two indexes.
Yes, there should be a correlation between the two indices. I would do the calculations again :)
Hi!
Another possibility is to go Hill numbers instead of shannon or simpson indices. They are considered more general (Simpson and shannon indices are essentially special cases of Hill numbers) and avoid a number of problems with those two indices.
You can check a nice introduction to the subject here:
Article A conceptual guide to measuring species diversity
And papers therein (in particular from Jost and or Chao) will help you go further.
Good luck!
Nicolas
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