Abstract
Understanding how periodical disturbances affect the community assembly processes is vital for predicting temporal dynamics in microbial communities. However, the effect of dilutions as disturbances are poorly understood. We used a marine bacterial community to investigate the effect of disturbance (+/−) and carrying capacity (high/low) over 50 days in a dispersal-limited 2 × 2 factorial study in triplicates, with a crossover in the disturbance regime between microcosms halfway in the experiment. We modelled the rate of change in community composition between replicates and used this rate to quantify selection and ecological drift. The disturbed communities increased in Bray–Curtis similarity with 0.011 ± 0.0045 (Period 1) and 0.0092 ± 0.0080 day−1 (Period 2), indicating that selection dominated community assembly. The undisturbed communities decreased in similarity at a rate of −0.015 ± 0.0038 day−1 in Period 1 and were stable in Period 2 at 0.00050 ± 0.0040 day−1, suggesting drift structured community assembly. Interestingly, carrying capacity had minor effects on community dynamics. This study is the first to show that stochastic effects are suppressed by periodical disturbances resulting in exponential growth periods due to density-independent biomass loss and resource input. The increased contribution of selection as a response to disturbances implies that ecosystem prediction is achievable.
Highlights
Understanding how ecological assembly processes create temporal patterns in community composition is a major goal in community ecology [1]
Estimation of selection and drift on community composition We developed a new approach to quantify the contribution of selection and drift during succession in highly controlled experimental settings where dispersal and speciation can be negligible (Fig. 1)
All 13 OTUs classified as Colwellia and all 5 OTUs classified as Vibrio had higher abundance during disturbance. This was not the case for all the DISCUSSION Predicting community responses to ecosystem changes is essential for improving ecosystem management
Summary
Understanding how ecological assembly processes create temporal patterns in community composition is a major goal in community ecology [1]. These are selection, ecological drift, dispersion, and diversification [4, 5]. These four processes have a varying degree of stochasticity and determinism. Selection is deterministic and based on differences in the fitness between populations. This process includes environmental filtering and biological interactions, such as competition and mutualisms. Dispersion and diversification are two processes that are both stochastic and deterministic. The relative contribution of these four processes on community assembly can vary between sites and changes over time [7, 8]
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