Fig. 2

Schematic explaining the relationship between microbiome composition, diversity indices (richness, Shannon index and Simpson index), Hill numbers ^qD (a) and diversity profiles for four theoretical systems (b). Figure adapted from [30]. For sample 1 and sample 4, all amplicon sequence variants (ASVs) are evenly distributed, so Hill numbers of all orders of diversity (q) stay the same within sample 1 and sample 4. As sample 4 has half the amount of equally abundant ASVs to sample 1, Hill numbers also half, in contrast to the Shannon index or Simpson index. At q = 0, only richness is considered, ignoring relative abundance. Consequently, for q = 0, Hill numbers for samples 1, 2 and 3 are the same. For q > 0, Hill numbers decrease as the importance attributed to abundant ASVs increases. As sample 3 is dominated by 5 ASVs, Hill numbers ¹D and ²D approximate 5. The diversity profile (b) shows the number of ASVs and evenness of the four theoretical systems. A flat profile indicates evenness