To understand how extreme halophiles respond to recurrent disturbances, we challenged the communities thriving in salt-saturated (~36% salts) ~230 L brine mesocosms to repeated dilutions down to 13% (D13 mesocosm) or 20% (D20 mesocosm) salts each time mesocosms reached salt saturation due to evaporation (for 10 and 17 cycles, respectively) over 813 days. Depending on the magnitude of dilution, the most prevalent species, Haloquadratum walsbyi and Salinibacter ruber, either increased in dominance by replacing less competitive populations (for D20, moderate stress conditions), or severely decreased in abundance and were eventually replaced by other congeneric species better adapted to the higher osmotic stress (for D13, strong stress conditions). Congeneric species replacement was commonly observed within additional abundant genera in response to changes in environmental or biological conditions (e.g. phage predation) within the same system and under a controlled perturbation of a relevant environmental parameter. Therefore, a genus is an ecologically important level of diversity organization, not just a taxonomic rank, that persists in the environment based on congeneric species replacement due to relatively high functional overlap (gene sharing), with important consequences for the success of the lineage, and similar to the success of a species via strain-replacement. Further, our results showed that successful species were typically accompanied by the emergence of their own viral cohorts, whose intra-cohort diversity appeared to strongly covary with, and likely drive, the intra-host diversity. Collectively, our results show that brine communities are ecologically resilient and continuously adapting to changing environments by transitioning to alternative stable states.

中文翻译：

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受到反复渗透干扰的极端嗜盐菌的生态成功主要是由同系物种替换驱动的


为了了解极端嗜盐菌如何对反复出现的干扰做出反应，我们挑战了在盐饱和（~36% 盐）~230 L 盐水中层中繁荣的群落，以重复稀释至 13%（D13 中层）或 20%（D20 中层）盐，每次中层由于蒸发（分别为 10 和 17 个循环）而达到盐饱和在 813 天内。根据稀释的大小，最普遍的物种 Haloquadratum walsbyi 和 Salinibacter ruber 要么通过取代竞争性较弱的种群（对于 D20，中等胁迫条件）而增加优势，要么丰度严重下降，最终被其他更适应较高渗透胁迫的同系物种所取代（对于 D13，强胁迫条件）。在同一系统内，响应环境或生物条件的变化（例如噬菌体捕食），并在相关环境参数的受控扰动下，通常在其他丰度属中观察到同属物种替换。因此，属是生态学上重要的多样性组织层次，而不仅仅是一个分类等级，由于相对较高的功能重叠（基因共享），它基于同源物种替换在环境中持续存在，对谱系的成功具有重要影响，类似于物种通过菌株替换的成功。此外，我们的结果表明，成功的物种通常伴随着他们自己的病毒队列的出现，其队列内的多样性似乎与宿主内部的多样性强烈共变，并可能推动宿主内部多样性。总的来说，我们的结果表明，盐水群落具有生态弹性，并通过过渡到替代稳定状态来不断适应不断变化的环境。