What is Alpha Diversity (Shannon Index)?
Alpha diversity summarises how many distinct microbial taxa are present in a single stool specimen and how evenly their relative abundances are distributed. The Shannon index weights both richness and evenness, so a community dominated by a few taxa scores lower than one in which many taxa coexist at comparable abundance. In adults, a more diverse gut community is broadly associated with ecological stability and resilience to perturbation, though diversity is a population-level correlate rather than a mechanistic readout for any one person.