```r
head(taxa.roles)

                                        z         p          roles
Dietzia                        -0.9114654 0.0000000 provincial hub
Streptomyces                   -0.9114654 0.0000000 provincial hub
Brumimicrobium                 -0.9114654 0.0000000 provincial hub
Nitrosomonas                    0.6076436 0.0000000 provincial hub
Sphingobacterium                0.6076436 0.0000000 provincial hub
unclassified_Flavobacteriaceae -0.1519109 0.4444444  connector hub
```