Hi,
mantel statistics has repeatedly been criticized. I wonder if there is an (approved) alternative for my problem:
I aim to test whether one parameter (productivity, P) affects turnover (t) among ecological communities in time (T) or space (S).  (ΔT and ΔS will be used as a co-variables).
To avoid confusion - I do NOT aim to test whether P affects composition as such (which could be tested by an ordination method), but whether the degree of similarity among samples scales with P.
 My approach so far was to calculate a dissimilarity matrix from my community data, distance matrices for the relevant environmental data (ΔT, ΔS, ΔP) and a mean (P) matrix, giving the mean(P) for each pair of observations.
The I performed mantel tests whether t correlates with mean(P), taking other variables into account (partialing out). However, mantel and especially partialing out are often criticized (e.g. see documentation in vegan). 
any views?
thanks!
Robert


Robert Ptacnik, PhD

ICBM, Univ. of Oldenburg
Schleusenstrasse 1, DE-26382 Wilhelmshaven
http://www.icbm.de/planktologie/en/
  
ptacnik@icbm.de
FON +49 4421 944-205
FAX +49 4421 944-299
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