Alternative states by the difference of medium condition and the ecological stochasticity

Understanding ecosystem transition processes and their functions is becoming increasingly important. Focusing on community assembly, the theory of biological communities, which states that the processes that determine community structure can be divided into four main higher-order processes: selection, drift, speciation, and dispersal, has attracted much attention in recent years. If only traits and populations are taken into account, while selection is described by deterministic model, the expected fluctuations in the number of individuals in each process, the random dispersal or their order and drift due to random births and deaths are described by stochastic model. While both empirical and theoretical studies suggest that stochastic dispersal is involved in important phenomena such as the emergence of alternative stable states, the impact of drift is largely understudied. In this study, we investigated the effects of selection and drift in microbial communities with multiple replications using high-throughput culture using microbial systems and community structure identification using illumine system. The results showed that there are conditions under which drift is strongly effective and conditions under which it is not, and that for some conditions, drift can generate large differences at the family level community structure. In the future, more detailed experimental systems and models should be used to investigate the emergence of stochastic community fluctuations caused by drift.