Disturbance Regimes Predictably Alter Diversity in an Ecologically Complex Bacterial System

Abstract

Diversity is often associated with the functional stability of ecological communities from microbes to macroorganisms. Understanding how diversity responds to environmental perturbations and the consequences of this relationship for ecosystem function are thus central challenges in microbial ecology. Unimodal diversity-disturbance relationships, in which maximum diversity occurs at intermediate levels of disturbance, have been predicted for ecosystems where life history tradeoffs separate organisms along a disturbance gradient. However, empirical support for such peaked relationships in macrosystems is mixed, and few studies have explored these relationships in microbial systems. Here we use complex microbial microcosm communities to systematically determine diversity-disturbance relationships over a range of disturbance regimes. We observed a reproducible switch between community states, which gave rise to transient diversity maxima when community states were forced to mix. Communities showed reduced compositional stability when diversity was highest. To further explore these dynamics, we formulated a simple model that reveals specific regimes under which diversity maxima are stable. Together, our results show how both unimodal and non-unimodal diversity-disturbance relationships can be observed as a system switches between two distinct microbial community states; this process likely occurs across a wide range of spatially and temporally heterogeneous microbial ecosystems.

Frequency of disturbance alters diversity, function, and underlying assembly mechanisms of complex bacterial communities

“…In contrast, intermediate levels either increased or maintained the same 2 D over time (after an initial decrease within the first two weeks), seemingly a case where niche overlap promoted stochastic assembly (10). The emergence of a IDH pattern after time is coherent with findings in previous microcosm studies using synthetic protist (56) and freshwater enrichment (35) microbial communities. Yet, none of these studies evaluated the relative importance of the underlying assembly mechanisms of assembly on the observed diversity dynamics.…”

“…The IDH has been influential in ecological theory, as well as in management and conservation (32), but its predictions do not always hold true (27, 33). For example, in soil and freshwater bacterial communities different patterns of diversity were observed with increasing disturbance frequency with biomass destruction (34) and removal (35) as disturbance type, respectively. Meanwhile, the effect of varying frequencies of non-destructive disturbances on bacterial diversity remains unknown.…”

Microbial communities across nearshore to offshore coastal transects are primarily shaped by distance and temperature

“…2 and Supporting Information Fig. S5), which could be attributed to increases in resource types and concentrations (Waide et al, 1999), and fluctuating environmental conditions which promotes co-existence within the bacterioplankton (Hutchinson, 1961;Gibbons et al, 2016). However, in spite of greater environmental variability closer to shore (e.g.…”

Do composition and diversity of bacterial communities and abiotic conditions of spring water reflect characteristics of groundwater ecosystems exposed to different agricultural activities?

“…This finding likely results from the fact that Shannon diversity is equally sensitive to rare and abundant species, whereas Simpson's diversity index is more sensitive to abundant species (Morris et al, 2014;Vuono et al, 2015). According to the intermediate disturbance hypothesis (Connell, 1978), disturbance prevents competitive species from dominating a given habitat while enabling space for colonization of less competitive species (Gibbons et al, 2016), which is why an increase in the number of rare species is indicative of disturbance (Piper, Siciliano, Winsley, & Lamb, 2015). Furthermore, circumstantial support for disturbance is the fact that the disturbance-tolerant phylum, Bacteriodetes (Kim, Heo, Kang, & Adams, 2013), compose approximately 14% of bacterial communities sampled at spring BB3 ( Figure 4A), although differences were found to be significant only in comparison to spring BB4 (p = 0.03; Wilcoxon rank sum test).…”