Abstract
Environmental disturbances have long been theorized to play a significant role in shaping the diversity and composition of ecosystems. However, an inability to specify the characteristics of a disturbance experimentally has produced an inconsistent picture of diversity-disturbance relationships (DDRs). Here, using a high-throughput programmable culture system, we subjected a soil-derived bacterial community to dilution disturbance profiles with different intensities (mean dilution rates), applied either constantly or with fluctuations of different frequencies. We observed an unexpected U-shaped relationship between community diversity and disturbance intensity in the absence of fluctuations. Adding fluctuations increased community diversity and erased the U-shape. All our results are well-captured by a Monod consumer resource model, which also explains how U-shaped DDRs emerge via a novel 'niche flip' mechanism. Broadly, our combined experimental and modeling framework demonstrates how distinct features of an environmental disturbance can interact in complex ways to govern ecosystem assembly and offers strategies for reshaping the composition of microbiomes.
Highlights
Biodiversity is a cornerstone of ecosystem stability and function (Tilman et al, 2014)
We were intrigued because a U-shaped relationship between diversity and disturbance intensity does not agree with historical wisdom (Huston, 1979), U-shaped diversitydisturbance relationships (DDRs) have been reported for other disturbance characteristics such as frequency (Miller et al, 2011)
Advances in automated continuous culture technology and next-generation sequencing enabled laboratory microbial ecology studies to systematically dissect the role of environmental disturbance with fine resolution at scale
Summary
Biodiversity is a cornerstone of ecosystem stability and function (Tilman et al, 2014). While it is well appreciated that environmental changes influence species diversity in all ecosystems, the exact nature of this critical relationship is unclear. There have been many efforts aimed at understanding the role of environmental disturbances, which are perturbations to the state of an environment. These disturbances are of ecological interest for the impact they have on a community, for example, by bringing about mortality of organisms and a reduction of biomass of a community. Various diversity-disturbance (DDR) relationships have been proposed that draw intuition from observations of natural ecosystems. A famous example is the Intermediate Disturbance Hypothesis (Connell, 1978; Huston, 1979), in which species diversity peaks at intermediate disturbance intensities (Figure 1a). Earlier assertions that disturbance weakens or interrupts competition (Connell, 1978; Huston, 1979) have been refuted by both
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