Dr. Souza, If you haven't already, you should consider one of the many variations on redundancy analysis developed by Legendre and others. Legendre and Gallagher (2001 in Oecologia) suggest a hellinger transformation to abundance data, and then it is appropriate to use euclidean based techniques such as RDA for a constrained ordination. The software is available for R, some of it is in the vegan and ecodist packages, but there are some other packages that are useful for exploring diversity that aren't available from all of the R mirrors that I could point you toward, depending on the objective of you analysis.
If you are set on using non-euclidean distance measures, such as bray-curtis distances, you can use a distance based RDA analysis (dbRDA) which is explained in Legendre and Anderson (1999) in Ecological Mongraphs. I hope my suggestions are useful. -Eric --------------------------------------------------- Eric R. Sokol Department of Biological Sciences Virginia Tech Blacksburg, VA 24061-0406 [email protected] --------------------------------------------------- On Sun, Jul 19, 2009 at 11:34 AM, Alexandre F. Souza<[email protected]> wrote: > Hello All, > > Do anyone has ever performed a constrained NMDS with community data? I > have read in McCune and Graces' Analysis of Ecological Communities that > the theory of such analysis already exists (i.e., associating vectors of > environmental variables to a NMDS ordination) but has seldon been used > by ecologists. It would be a better alternative to CCA, which has > stingent premises that ecological data does not match properly most of > times. > > I suppose that this could be implemented in R, but I could not find it > in Vegan or other packages. > > Thanks in advance, > > Alexandre > > > > Dr. Alexandre F. Souza > Programa de Pós-Graduação em Biologia: Diversidade e Manejo da Vida > Silvestre > Universidade do Vale do Rio dos Sinos (UNISINOS) > Av. UNISINOS 950 - C.P. 275, São Leopoldo 93022-000, RS - Brasil > Telefone: (051)3590-8477 ramal 1263 > Skype: alexfadigas > [email protected] > http://www.unisinos.br/laboratorios/lecopop > > -- > Esta mensagem foi verificada pelo sistema de antivírus e > acredita-se estar livre de perigo. >
