SHE analysis

Theory behind mothur
1

I am currently working with biofilms obtained from a brevery enviroment. When analyzing my data with the collect.single or rarefaction.single command i observed an constant Shannon-Index even at a small sample size with low evenness values. So far nothing to be worry about. Next i was curious about the proportion of richness and evenness on the Shannon-Index at the different sample sizes. Itried to use the SHE analysis method based on Buzas and Hayek which uses the formula:

H(Shannon)= lnE + lnS

I compared the sum of the lnE- and lnS-values with the Shannon-Index obtained by mothur and found that they differ. For example i obtained 48 OTU´s and E=0,3361. The Shannon-Index calculated by mothur is 1,3301 but my calculation with the formula above is 2,78. Do you have any experience with this?

Thanks in advance

Andre

2

Using the shannon index, evenness is calculated as shannon/ln(S). I’m not familiar with “SHE analysis” and my rules of logarithms are a bit rusty, but I don’t know how you get from E=H/ln(S) to H=ln(E) + ln(S)

3

My fault…

This formula just works if you are analyzing a given community, e.g watching the changes for a given set of species. If new species steadily approach the formula make now sense (as you assumed).

By the way, thank you for providing the mothur-software and for the support.

Have a nice weekend.

Andre