Alternative states by the difference of medium condition and the ecological stochasticity. mixed culture metagenome

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.

理解生态系统转变过程及其功能的重要性日益凸显。聚焦群落组装（community assembly）领域，生物群落理论（theory of biological communities）指出，决定群落结构的过程可划分为四大高阶过程：选择（selection）、漂变（drift）、物种形成（speciation）与扩散（dispersal），该理论近年来受到广泛关注。若仅考量性状与种群，且以确定性模型（deterministic model）刻画选择过程，则需借助随机模型（stochastic model）描述各过程中个体数量的预期波动、随机扩散（random dispersal）及其作用顺序，以及由随机出生与死亡事件引发的漂变。尽管实证与理论研究均表明，随机扩散参与了替代稳定态（alternative stable states）出现等重要生态现象，但漂变的影响迄今仍未得到充分研究。本研究以微生物系统为依托，设置多重复实验，采用高通量培养（high-throughput culture）结合Illumina系统开展群落结构鉴定，探究了微生物群落中选择与漂变的作用效应。研究结果表明，漂变的作用存在条件依赖性：在部分情境下漂变效应显著，而在另一些情境下则不明显；且在特定条件下，漂变可引发科水平（family level）群落结构的显著差异。未来需借助更精细的实验系统与模型，深入探究由漂变引发的随机群落波动的产生机制。