Biodiversity and ecosystem functioning in predator-prey communities

Once regarded as little more than simple model systems, microbial communities are now understood to drive major earth processes and patterns of biodiversity. In order to more fully understand them, there is a need to investigate the mechanisms that determine the structure and function of microbial systems. Predator-prey interactions have been studied for a long time in macroecological systems and are known for their role in determining community structure and dynamics. Functional diversity has come to the fore of ecology to take a central role in understanding what links species to biodiversity and ecosystem function. In this thesis I investigated the biodiversity and ecosystem functioning of microbial predator-prey communities. I used naturally occurring bacterial communities in combination with co-occurring heterotrophic protists to perform manipulative experiments to investigate: a) the functional diversity of heterotrophic protists and their interactive contributions to ecosystem functioning; b) the effects of bacterial prey community diversity and composition on these attributes of protists; and c) the role of functional diversity in maintaining protist community diversity. I found that not only is it possible to classify functional diversity by species interactions, but that the effects of prey community diversity and composition highlight the flexible nature of this property, particularly in predators. I also found evidence of negative biodiversity-functioning relationships and strong competitive interactions among heterotrophic protists. However, their functional diversity allowed them to maintain higher diversity in disturbed environments. Taken together, my thesis has advanced the understanding of the role of predator-prey interactions and functional diversity in regulating interactions and ecosystem functioning in microbial systems.