I'm doing partial distance based (db-)RDA analysis of nematode community data. I have got the triplots already. They contain vectors of environmental data.
Is it possible to overlay a second set of vectors, describing the relationship of biodiversity/nematode community Indices with community structure of the sites? Or do i have do perform a second db-RDA with these Indices as explanatory variables, and hence replace the environmental data for these Indices. Or is the use of Biodiversity indices, calculated on the basis of species communities, to explain these communities a circle reasoning?