[R-sig-eco] Dissimilarity for ordination of rank data

[Tania Bird]

Hi all,

I have a data set of species data in different sites but instead of
abundances, the presence has been converted to a rank score site-species
matrix. The ranks are calculated based on max-scores that have been log
transformed ln(x+1).
0 = absent and 5 = highest abundance for that species relative to other
sites and other species.

I would like to carry out multivariate analyses on this data such as PCA /
PCoA  RDA/Variation partitioning.
I assume no transformation is needed for this data since they are already
ranks.

My questions are :
*1) What is the best dissimilarity measure to use for this rank data?*
I read that Gower's distance *gowdis()* in {FD} or *daisy()* in {cluster}
 may be good choices?

*2) Is it appropriate to conduct RDA on rank data? *
Is an there a better alternative?

As a bonus question - can I treat these data the same as I would abundance
data in more advanced analyses such as beta-diversity analyses (e.g.*
betadisper()
in {vegan} ) *or  spatial eigenvector mapping (e.g. *dbMEM / AEM in
{adespatial}* )?


Many thanks

Tania

Tania Bird MSc
PhD Student: Coastal dune biodiversity conservation in Nizzanim LTER
Dept. of Geography & Environmental Development,
Ben Gurion University, Beer Sheva
https://www.linkedin.com/in/taniabird

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