I was having the same issue and the following code to visualize Mothur distance matrix:
col.names <- unlist(read.table("dist.dist", nrow = 1, as.is = TRUE))
df <- as.matrix(read.table("dist.dist", fill = TRUE, skip = 1,
row.names = 1))
dist = read.dist("dist.dist",diag=1)
x1 <- as.dist(as(dist, "matrix"))
X11()
hc = hclust(x1 )
plot(hc)
heatmap(as.matrix(x1))
dst <- data.matrix(x1)
library(MASS)
library(ggplot2)
library(ggrepel)
NMDS=metaMDS(dst, # Our distance matrix
k=2) # The number of reduced dimensions
stressplot(NMDS)
plot(NMDS)
ordiplot(NMDS,type="n")
orditorp(NMDS,display="sites",col="red",air=0.01)
Once you have NMDS result object (or CCA etc,.) it is quite straight forward