Fig. 2.

Phylogenetically conserved diets, geographic locations, or flying abilities partially contribute to phylosymbiosis in the gut microbiota of mammals, but not birds. For both mammals and birds, we compared the estimated level of phylosymbiosis (mean λ value represented by a diamond) to levels of phylosymbiosis (λ values within boxplots) estimated when shuffling the species that have the same diet, geographic location, flying ability (flying or nonflying), or combination of the latter traits. For each shuffling strategy, we performed 100 randomizations. Combining all traits strongly constrains the possible permutations, which may consequently retain a phylogenetic signal in the shuffling and lead to high λ values although the traits are actually not strongly contributing to phylosymbiosis.