[R] Vegan: how to plot sites labes in diversity plot

[Alejo C.S.]

Dear List,

I can'f figure how to add point labels in the next plot (example from
?taxondive help page, from vegan package):

library(vegan)
data(dune)
data(dune.taxon)
taxdis <- taxa2dist(dune.taxon, varstep=TRUE)
mod <- taxondive(dune, taxdis)
plot(mod)

The points in this plot are diversity values of single sites, and I'd
like to add a label to each one. The plot command don't accept a
"label" argument.
Any tip?

Thanks in advance.