British bacteria. Similar colours are similar bacterial communities. From Griffiths et al. 2011.

There is an endless variety of life on Earth. One of the main jobs of ecologists and evolutionary biologists is to understand how this biodiversity was created and how it is maintained over time. This is especially relevant in the microbial world: new DNA sequencing technologies have only just allowed us to survey microbial diversity in nature. This work has shown that the vast majority of biodiversity is microbial, so understanding how communities of microbes operate is particularly challenging. Every drop of puddle water is more diverse than a tropical forest.

Much of our research is concerned with understanding the ecological and evolutionary processes that change the composition (which species) and diversity (how many species) of microbial communities over space and time.

We have used a variety of approaches to tackle this question. At the largest scale, we have surveyed microbial communities from across the UK to map how they change in space. At the micro-scale, we have documented how manipulating individual ecological factors (such as dispersal rates among sites) alters spatial patterns and temporal dynamics.

Does biodiversity matter?

Experimentally altering the biodiversity (species richness) of bacterial communities results in increasing production of carbon dioxide from the community as a whole. From Bell et al. (2005).

Communities of organisms produce outputs: many heterotrophs respire carbon dioxide, bacteria in sewage treatment plants degrade harmful pollutants, bees pollinate flowers and crops.  These outputs and their stability can be broadly defined as measurements of  ‘ecosystem functioning’. Ecosystem functioning can be harmful, beneficial  (often called ‘ecosystem services’), or neutral to humans. We are interested in how changes to community composition and diversity influence ecosystem functioning. The simple experiment that we have performed is to construct communities that differ in their composition and their diversity while measuring ecosystem outputs, such as the total amount of carbon dioxide respired from the community.Such manipulations typically result in increasing functioning with increasing numbers of species. We have conducted many similar experiments with increased throughput by using robots to assemble the communities. We have been able to show how these patterns evolve due to the constantly-changing interactions among species within the community.