When timescales meet: Microbiome dynamics is influenced by hosts’ life-history.

Microbial life is highly abundant in the biosphere. Macroscopic lifeforms are no exception. We harbor a large number of microorganisms in different parts of our bodies, often referred to as the microbiome. What separates us from abiotic habitats is that we undergo life-cycles. We have developed stochastic models to understand the consequences of host life-history on the ecology of the microbiome. Particularly, we focus on the effect of the host lifespan and initial microbiome. Our results point at the limits imposed by life-history, but also at the diverse dynamics, even in contexts free of selection at the level of microbes and hosts. Multiple reported experimental observations in organisms like nematodes, fruit flies, and zebrafish can be unified around colonization. These include the emergence and coexistence of alternative microbiome states, the persistence of microbe-free hosts, and the inconsistent occurrence of microbial types.