[R] p-value for Nonmetric Multidimentional Scaling?

[Michael Denslow]

Dear R-helpers,

I am running metaMDS in the vegan package, which uses isoMDS in MASS, to perform Nonmetric Multidimentional Scaling (NMDS).

I have seen some authors report a p-value for the NMDS ordination based on randomization of the dataset. As I understand it this is meant to compare the stress in your dataset to multiple runs of randomized data.
I do not see a way to perform such a test in vegan or MASS.

So my questions are:
Is this necessary? and Does R have a function to do this?

Thanks in advance for your help,
Michael