Вот простое решение
library(vegan)
#I suppose your data is something like this
df<-data.frame(Sites = paste("Tech",1:20),
Sp1 = rep(c(1,0),each=10),
Sp2 = rep(c(1,0,0,1),each=5),
Sp3 = rep(c(0,1,0,1),each=5))
#Change df from data.frame to numeric matrix, excluding the first column
mat<-data.matrix(df[,-1])
#Add first column as row names
row.names(mat)<-df[,1]
#Apply specaccum function
specaccum(mat)