Analysis of community ecology data in R

vltava.spe <- read.csv2 ('http://www.davidzeleny.net/anadat-r/data-download/vltava-spe.csv', row.names = 1)
vltava.env <- read.csv2 ('http://www.davidzeleny.net/anadat-r/data-download/vltava-env.csv', dec = '.')
plot (specnumber (vltava.spe) ~ vltava.env$pH.H, xlab = 'soil pH', ylab = 'Number of species')