[R-sig-eco] using Adonis for zero data

[Emma Stone]

Dear All,

I am running a multivariate ANOVA based on dissimilarities using the adonis 
function in the VEGAN package in R. I have trying to assess the number and 
types of bat mitigation used at sites as a function of three predictors. 
The predictors are : number of bats (nobats= continuous), impact (factor 
with 3 categories) and roost type(rtype = factor with 5 categories). There 
are three responses which are count data: number of boxes, number of barns 
and number of lofts.
The problem is that I have a lot of zeros in the data and they are not all 
integers.

I have been running the following code using euclidean distances but I am 
not sure that it is ok to use Euclidean distances for count data with 
zeros.

adonis(resp~Impact+nobats+rtype,data=pred,method=euclidean,permutation=500)

I have read that you can transform the distances with the following code
dis <- vegdist(decostand(resp, "norm"), "euclid")

so have done this and I do get a very difference result, but again I am not 
sure that this is suitable.

I have tried running the model with different distance measures but it will 
only run with the euclidean distance method.

Any help would be most appreciated.

Thanks

Emma


----------------------
Emma Stone
Postgraduate Researcher
Bat Ecology and Bioacoustics Lab
& Mammal Research Unit
School of Biological Sciences,
University of Bristol, Woodland Road,
Bristol, BS8 1UG
Email: emma.stone at bristol.ac.uk