Biodiversity and ecosystem functioning relationships in mega-diverse natural bacterial communities

Background/Question/Methods

In the last three decades, biodiversity has been shown to be an important driver of ecosystem functioning throughout a large variety of ecosystems, including terrestrial, marine and limnic examples. Biodiversity has been found to increase ecosystem functioning on average, to increase the temporal stability of the latter and to increase the community resilience. However, the median number of species typically manipulated in the studies was low and it is largely unknown if, and if so to which extend the biodiversity ecosystem function (B-EF) relationships hold true in megadiverse systems like natural bacterial communities. Here I present an experiment in which we studied functioning of 11 subsequent dilutions of 4 natural bacterial lake communities. The dilution series where incubated 6 weeks outdoors under light-exclusion and sampled every other day for biomass and 3 times, after 2, 4 and 6 weeks for realized diversity and carbon utilization patterns.

Results/Conclusions

The dilution-to-extinction approach resulted in a diversity gradient ranging from 25 to 3224 OTUs per sample in the full dataset and from 57 to 531 OTUs in the rarefied dataset (down-sampled to 4000 reads). Biomass was weakly positively correlated to Shannon diversity but neither the number of carbon sources that the community could utilize nor the uptake rates were correlated to any of the calculated diversity metrics, including richness, Shannon diversity and evenness. In summary we found some hints of a positive B-EF relationship but further investigation is needed in order to validate the theory and to get a better understanding of the ecological importance of extremely high diversity and the role of rare species.