Human activities and climate change are altering biodiversity. This means species compete more often for food (resources) with new, different species, and we need to anticipate how they evolve in response to these changes. Most studies of evolution are however based on species alone – but how does the presence of other species alter evolution? This week, in a work published in the scientific journal Ecology and Evolution, Charlotte Briddon, lead author of the study, tried to address this question.

In work supervised by Giulia Ghedini, group leader at the GIMM Foundation, the team of researchers tracked the evolution of three species of marine microalgae in the laboratory. Each of these species evolved either alone or in the presence of the other species. Microalgae are very useful to study evolution in real time because they are tiny and reproduce fast. They are also very important for marine ecosystems because they produce oxygen and are food for fish.

With these experimental settings, the team made two key discoveries. First, they found that species evolved in the same way, whether they evolved alone or with other species – possibly because they compete for very similar resources. A key ecologist, Robert MacArthur, predicted this outcome decades ago but this prediction was never tested experimentally, until now.

Second, they observed that some key traits evolved in the same way for all three species, indicating that evolution might be predictable. Specifically, the team identified consistent changes in the way algal cells produce energy for growth when they are exposed to intense competition: the evolved algal cells were capable of increasing the production of energy (via photosynthesis) without increasing the amount of energy spent (through respiration). This was particularly observed when resources were scarce. The final outcome of this adaptation was that cells had more energy available and could grow faster when competition was intense – making them better adapted to competitive environments.

When asked about what motivated the researchers to pursue this study, Charlotte shared that she is interested “in understanding how communities and therefore, ecosystems function, especially in our ever-changing world. As phytoplankton are the base of the marine food chain, it is critical to understand how they will be impacted by the conditions predicted in the future. This work is one of the first studies to investigate how species change in response to competition, an important building block to comprehending complex real-world processes.” The lab led by Giulia Ghedini is the right place to develop these studies, as both researchers share the same motivation. For Giulia, the main drive is “ to understand how species interact, and how their interactions determine what ecosystems look like and how they function. This is particularly important today because our society is changing nature at a very rapid pace. Critically, species can also change (evolve) rapidly.” About the relevance of this work, Giulia Ghedini adds that “this work gives us some important insights into how species evolve when they interact with multiple competitors – these results give us one more piece of the puzzle to understand how these processes happen in the (much more complex) real world.”