Dataset Information

Effects of dispersal and selection on stochastic assembly in microbial communities.

ABSTRACT: Stochastic processes can play an important role in microbial community assembly. Dispersal limitation is one process that can increase stochasticity and obscure relationships between environmental variables and microbial community composition, but the relationship between dispersal, selection and stochasticity has not been described in a comprehensive way. We examine how dispersal and its interactions with drift and selection alter the consistency with which microbial communities assemble using a realistic, individual-based model of microbial decomposers. Communities were assembled under different environmental conditions and dispersal rates in repeated simulations, and we examined the compositional difference among replicate communities colonizing the same type of leaf litter ('within-group distance'), as well as between-group deterministic selection. Dispersal rates below 25% turnover per year resulted in high within-group distance among communities and no significant environmental effects. As dispersal limitation was alleviated, both within- and between-group distance decreased, but despite this homogenization, deterministic environmental effects remained significant. In addition to direct effects of dispersal rate, stochasticity of community composition was influenced by an interaction between dispersal and selection strength. Specifically, communities experiencing stronger selection (less favorable litter chemistries) were more stochastic, possibly because lower biomass and richness intensified drift or priority effects. Overall, we show that dispersal rate can significantly alter patterns of community composition. Partitioning the effects of dispersal, selection and drift based on static patterns of microbial composition will be difficult, if not impossible. Experiments will be required to tease apart these complex interactions between assembly processes shaping microbial communities.

SUBMITTER: Evans S

PROVIDER: S-EPMC5315486 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature

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Effects of dispersal and selection on stochastic assembly in microbial communities.

Evans Sarah S Martiny Jennifer B H JB Allison Steven D SD

The ISME journal 20160805 1

Stochastic processes can play an important role in microbial community assembly. Dispersal limitation is one process that can increase stochasticity and obscure relationships between environmental variables and microbial community composition, but the relationship between dispersal, selection and stochasticity has not been described in a comprehensive way. We examine how dispersal and its interactions with drift and selection alter the consistency with which microbial communities assemble using ...[more]

PMID: 27494293

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Project description:ABSTRACT The processes and mechanisms of community assembly and its relationships to community functioning are central issues in ecology. Both deterministic and stochastic factors play important roles in shaping community composition and structure, but the connection between community assembly and ecosystem functioning remains elusive, especially in microbial communities. Here, we used microbial electrolysis cell reactors as a model system to examine the roles of stochastic assembly in determining microbial community structure and functions. Under identical environmental conditions with the same source community, ecological drift (i.e., initial stochastic colonization) and subsequent biotic interactions created dramatically different communities with little overlap among 14 identical reactors, indicating that stochastic assembly played dominant roles in determining microbial community structure. Neutral community modeling analysis revealed that deterministic factors also played significant roles in shaping microbial community structure in these reactors. Most importantly, the newly formed communities differed substantially in community functions (e.g., H2 production), which showed strong linkages to community structure. This study is the first to demonstrate that stochastic assembly plays a dominant role in determining not only community structure but also ecosystem functions. Elucidating the links among community assembly, biodiversity, and ecosystem functioning is critical to understanding ecosystem functioning, biodiversity preservation, and ecosystem management. IMPORTANCE Microorganisms are the most diverse group of life known on earth. Although it is well documented that microbial natural biodiversity is extremely high, it is not clear why such high diversity is generated and maintained. Numerous studies have established the roles of niche-based deterministic factors (e.g., pH, temperature, and salt) in shaping microbial biodiversity, the importance of stochastic processes in generating microbial biodiversity is rarely appreciated. Moreover, while microorganisms mediate many ecosystem processes, the relationship between microbial diversity and ecosystem functioning remains largely elusive. Using a well-controlled laboratory system, this study provides empirical support for the dominant role of stochastic assembly in creating variations of microbial diversity and the first explicit evidence for the critical role of community assembly in influencing ecosystem functioning. The results presented in this study represent important contributions to the understanding of the mechanisms, especially stochastic processes, involved in shaping microbial biodiversity.

Project description:Microbial communities can be structured by both deterministic and stochastic processes, but the relative importance of these processes remains unknown. The ambiguity partly arises from an inability to disentangle soil microbial processes from confounding factors, such as aboveground plant communities or anthropogenic disturbance. In this study, we characterized the relative contributions of determinism and stochasticity to assembly processes of soil bacterial communities across a large environmental gradient of undisturbed Antarctic soils. We hypothesized that harsh soils would impose a strong environmental selection on microbial communities, whereas communities in benign soils would be structured largely by dispersal. Contrary to our expectations, dispersal was the dominant assembly mechanism across the entire soil environmental gradient, including benign environments. The microbial community composition reflects slowly changing soil conditions and dispersal limitation of isolated sites. Thus, stochastic processes, as opposed to deterministic, are primary drivers of soil ecosystem assembly across space at our study site. This is especially surprising given the strong environmental constraints on soil microorganisms in one of the harshest environments on the planet, suggesting that dispersal could be a driving force in microbial community assembly in soils worldwide. IMPORTANCE Because of their diversity and ubiquity, microbes provide an excellent means to tease apart how natural communities are structured. In general, ecologists believe that stochastic assembly processes, like random drift and dispersal, should dominate in benign environments while deterministic processes, like environmental filtering, should be prevalent in harsh environments. To help resolve this debate, we analyzed microbial community composition in pristine Antarctic soils devoid of human influence or plant communities for eons. Our results demonstrate that dispersal limitation is a surprisingly potent force of community limitation throughout all soil conditions. Thus, dispersal appears to be a driving force of microbial community assembly, even in the harshest of conditions.

Dataset Information

Effects of dispersal and selection on stochastic assembly in microbial communities.

Publications

Effects of dispersal and selection on stochastic assembly in microbial communities.

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