RT Journal Article SR Electronic T1 Environmental fluctuations reshape an unexpected diversity-disturbance relationship in a microbial community JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.07.28.225987 DO 10.1101/2020.07.28.225987 A1 Christopher P. Mancuso A1 Hyunseok Lee A1 Clare I. Abreu A1 Jeff Gore A1 Ahmad S. Khalil YR 2020 UL http://biorxiv.org/content/early/2020/11/30/2020.07.28.225987.abstract AB Environmental disturbances have long been theorized to play a significant role in shaping the diversity and composition of ecosystems1,2. However, fundamental limitations in our ability to specify the characteristics of a disturbance in the field and laboratory have produced an inconsistent picture of diversity-disturbance relationships (DDRs) that shape the structure of ecosystems3. Here, using a recently developed continuous culture system with tunable environmental control4, we decomposed a dilution disturbance into intensity and fluctuation components5,6, and tested their effects on the diversity of a soil-derived bacterial community across hundreds of replicate cultures. We observed an unexpected U-shaped relationship between community diversity and disturbance intensity in the absence of fluctuations, an observation counter to classical intuition. Adding fluctuations erased the U-shape and increased community diversity across all disturbance intensities. All of these results are well-captured by a Monod consumer resource model, which further reveals how U-shaped DDRs emerge based on a novel “niche flip” mechanism in which competitive outcomes flip and coexistence regimes subsequently collapse at intermediate disturbance levels. Broadly, our results demonstrate how distinct features of an environmental disturbance can interact in complex ways to govern ecosystem assembly and produce all the major classes of DDRs, without invoking other organizational principles. With these findings, we construct a unifying framework that reconciles the disparate DDRs observed in nature, and propose strategies for predictively reshaping the compositional complexity of microbiomes and other ecosystems.Competing Interest StatementThe authors have declared no competing interest.