[R] moving points labels in ordinations

[Peter Nelson]

I'm trying to place labels so as to avoid covering points (and other labels) in an ordination plot. I've been trying to use orditkplot() for this  purpose, but get an error message, even when I try to replicate the example: 

>require("vegan")
>data(varespec)
> ord <- cca(varespec)
> orditkplot(ord, mar = c(4,4,1,1)+.1, font=3)
Error in structure(.External(.C_dotTclObjv, objv), class = "tclObj") : 
  [tcl] invalid command name "tk".
In addition: Warning message:
In fun(libname, pkgname) : couldn't connect to display ":0"
> 

Any ideas? Thanks, Pete