Dynamics of community classes over time. (A-C) Subjects from different community classes switch to other community classes or maintain their original community class in different habitats: (A) retroauricular crease, (B) anterior nares, and (C) stool. The colored circles represent different community classes. The names of community classes are followed by the number of subjects belonging to the community classes at the first visit. Subjects transferring to other community classes at the second visit are indicated by arrows along with the number of subjects that switched. The number inside each community class indicates the number of subjects maintaining the same community class at the second visit.