The whole is greater than the sum of its parts: exploring the role of chemodiversity as a mediator of ecological processes in the landscape

For many years, ecologists have tried to understand the main drivers of interactions between organisms in nature. Examples of such interactions include herbivores feeding on their plant hosts, predators finding their prey, or flower-visiting insects finding the best nectar sources. Finding a partner is another examplary interaction that is crucial for most organisms. For humans, finding our resources has become increasingly simplified in the last centuries, and we often base our decisions on what is on display in the local supermarket, or what is available on the local farmer’s market. A potential life partner can be found wherever humans hang out and socialize, from a local restaurant, to schools, to the internet. Where we are likely to find food or mates has become very predictable. For most wild organisms, finding food or a partner is not as straightforward as going to the local store, or hanging out at the local pub. Most organisms, from female butterflies trying to find the right host plant to nourish their larvae - and this plant trying to do its very best to minimize the consequences - to vultures trying to find a decaying carcass to feed on, or male and female deer trying to find suitable mates each fall season; each organism needs to find their interaction partners in a very noisy environment. To succeed in this, they rely on a series of cues, including vision, touch, hearing, taste and smell.

Over the past century, it has become quite clear that many organisms rely on more than one sense to guide them towards a resource, towards a partner, or away from their enemies. However, across the tree of life, there is one thing that virtually all organisms have in common; they all consist of and produce countless chemical substances, and many of them produce specialized compounds to help them increase their odds in securing growth, survival, and reproduction. For this reason, most organisms also possess means to detect a broad range of chemicals, the ones produced by their own kind or by others. One could say that chemistry is a universal language. Chemicals can be very informative, even for humans, even without us realizing it. For instance, human smell can subconsciously foster bonding, for instance between mothers and their babies, or between two people figuring out whether they like each other. It also informs us of nutritional quality; think of the smell of a delicious soup, or the bad smell of milk gone bad. Chemistry helps organisms navigate through some of the toughest complexities of life, and hence is an essential component of life on Earth. Chemical ecologists realized that interactions between organisms are shaped not only by individual compounds, but also by the chemical diversity -chemodiversity- that emerges when they combine into a blend. The number of compounds and their relative concentrations, as well as how similar the compounds are from a chemistry point of view, contains important information that serves as a guide for species interactions. Still, the way chemical blends combine and interact with the environment in natural ecosystems is far less understood.

In the German Research Unit FOR3000 on ‘The Ecology and Evolution of Intraspecific Chemodiversity in Plants,’ funded by the German Research Foundation (DFG), several German research groups have joined forces to better understand the role of such processes, and the role they play in guiding plant interactions, for instance with microbes, herbivores and pollinators. The research unit has pushed the field of chemodiversity research forward since its initiation in 2020. The Research Unit’s latest review paper, now published in Nature Ecology and Evolution, originated during a FOR3000 annual meeting held at Helmholtz Munich in November 2024. In this review work, led by Dr. Maximilian Hanusch, Dr. Thomas Dussarrat, and Dr. Robin Heinen, the authors describe how chemical blends produced by different organisms from different parts of the tree of life enter their shared living environment, where they mix and form new blends, generating a dynamic chemodiversity landscape. The authors describe conceptually how the chemodiversity landscape changes in time and space, and how the position of the contributing organisms within the chemodiversity landscape impacts its form. They then describe how blends of different origins can lead to emergent properties. Do novel complex blends have properties that arise from the combined effect of compounds that do not arise for the compounds on their own? The authors present the ecological evidence for emergent properties in the chemodiversity landscape and discuss important questions and directions for future research that will help us understand the role of chemodiversity in the complexity of natural landscapes. 

Find the paper here at Nature Ecology and Evolution.