Assistant Professor Louisiana State University Baton Rouge, Louisiana, United States
Abstract: Biodiversity in microbial communities is shaped by ecological and evolutionary processes. Due to the large population size and short generation time of microorganisms, the role of evolution in shaping biodiversity can be especially significant. However, the temporal relationship between evolutionary changes and microbial diversity is not well understood. We hypothesize that the impact of evolution on microbial diversity increases over time. This is because it takes time for diversity to emerge via evolutionary processes. As such, we predict that the effects of evolution on microbial biodiversity will become more pronounced as time progresses.
To examine this hypothesis, we established laboratory microbial communities with the bacterium Pseudomonas fluorescens and six common environmental bacteria. In the wildtype of P. fluorescens, the bacterium evolves biofilm forming ability via mutations in three operons. In the strain with the three operons knockout, biofilm evolution is disabled. We manipulated the presence and absence of evolution by introducing either the wildtype or the knockout strain to the microbial communities and monitored the responses of bacterial species diversity to biofilm evolution over three weeks.
Biofilm evolution significantly influenced bacterial richness. Specifically, the wildtype strain more effectively reduced the abundance of other six competing bacteria than the strain with knockouts. The negative effect of evolution on total abundance translated into a decline in species diversity. Interestingly, we observed overshooting dynamics in P. fluorescens, with the abundance of biofilm-forming individuals increasing rapidly from the start of the experiment until day 14, after which it began to decline. As a result, the effect size of evolution on biodiversity peaked on day 14.
Taken together, these results demonstrate the temporal dependency of the effect of evolution on microbial biodiversity. Our findings highlight the importance of eco-evolutionary dynamics in shaping the biodiversity of microbial communities. By shedding light on the mechanisms that influence microbial diversity, our study contributes to a deeper understanding of the ecological and evolutionary processes that shape life on Earth.
