Relatedness and diversity of microbial communities. (A) Box-and-whisper plots of pairwise Bray-Curtis distances of the microbiomes of pediatric cystic fibrosis (CF) patients as a function of genetic relatedness, showing significantly more distance between unrelated patients than between related patients (P = 0.01), but no significant difference in relatedness between monozygotic (MZ) twins and nontwin siblings with CF (a proxy for dizygotic (DZ) twins, labeled “DZ Sibling”). Boxes indicate median values as the center line of each box, which spans the interquartile range. Whiskers demarcate 1.5× the interquartile range. These values reflect 70 pairwise comparisons among the samples from the ten unrelated subjects, and four pairwise comparisons among samples from the five siblings. (B) Boxplots comparing Shannon Diversity Index in all children with CF in this study and adults with CF reveal significantly lower diversity in adult versus the pediatric cohort (P = 0.001). Median Shannon Diversity Index value from adult patients in the Tunney et al. study  is shown as the red line, and the median Shannon Diversity Index score in adult patients reported by Zhao et al.  is shown as a blue line for comparison to our adult cohort. Whiskers denote 1.5 times the interquartile range defined by the box. Open circles denote outlier values outside this range. Significance codes: ‘***’ P < 0.001; ‘**’ P < 0.01.