Fig. 2: Alpha-diversity indices are significantly different between PD patients and controls.

Indices were calculated at the species level for each dataset. Results were then combined using a random-effect meta-analysis approach. The log-generalized Odds Ratios indicate the degree of variation of each index between controls and PD. The richness of the samples was estimated using the observed number of species and the indices Chao1, ACE, and Fisher’s alpha. To estimate evenness, which indicates how different the species abundances in a community are from each other, we used the Bulla and Simpson indices. Finally, we estimated dominance, which describes how much one or few species dominate the community, and rarity, which assesses the number of species with low abundance in the samples. The data suggest that the gut microbiota of PD patients is more diverse (higher richness) than controls and this is likely a consequence of an increase in rare taxa (rarity).