How to run the Kruskal-Wallis or Mann-Whitney Test in R

Question

Can anyone give me a hint on how to run the Kruskal-Wallis Test below?

My objective : Is there any significance of the growth (agg_rel_abund) of bacteria between Forest and Urban for each family.

The code I have tried in R : kruskal.test(Habitat ~ agg_rel_abund, data = my_data) but obviously I know that is wrong... because I didn't hit my objective..

Let me briefly explain about my data :

There are types of sample, which is F and W.

When the sample name start with F, it means the Habitat is from Urban.

When the sample name start with W, it means the Habitat is from Forest.

It is okay if want to perform Mann-Whitey Test, or any Non-Parametric Test too... as long as can get to know the significance of the growth (agg_rel_abund) of bacteria between Forest and Urban for each family.