Plant-mediated interactions between organisms
Plants play an important role in most terrestrial ecosystems, in which they serve as the basal resource for most of the higher trophic levels in the food chain. Plants are mostly sessile, and therefore, in contrast to most animals, have very few means to physically ‘fight or flight’. This does, however, not mean that plants have evolved to be sitting ducks, waiting to be devoured by anything that passes by. In fact, most plants have evolved a broad range of structural adaptations and chemical compounds to interact with their living environment. These can be used to keep away or deter antagonists, but also to keep close or attract beneficial organisms. Plants are highly plastic in both their structural and chemical properties, and hence, the environment plays an important role in a plant’s physical shape or health status. In the ‘Plant-mediated Interactions’ theme, we investigate how both biotic (e.g. multiple attackers) and abiotic factors (light pollution, climatic variation, pesticides) affect phytochemistry and plant growth (i.e., quality and quantity), and how the consequential changes in these properties affect other interactions occurring on the plant.
Artificial Light at Night (ALAN) effects on plants
Ongoing projects: Robin Heinen
Humans lit up the world. Over the course of the past century, we have introduced light into countless terrestrial and aquatic environments that traditionally experience prolonged stretches of darkness through the earth’s predictable day-night patterns. In many terrestrial ecosystems, man-made lamps are lighting up the night, and the problem of artificial light at night (ALAN) is still quickly expanding. It is evident from the research of the past two decades that ALAN has strong impacts on animals, for instance via sleep disruption, behavioral attraction or deterrence, or even impacts on physiology. In plants, it has long been clear that light is important, as a resource, and as a mediator of many signaling pathways. However, the research on the effects of ALAN on plants is limited. Several studies indicate effects of ALAN on phenological processes, and the insect food web, but there are only a small handful of studies that have investigated the effects of ALAN on plants and interactions with, or within the phytobiome. In this line of research, we study the effects of ALAN on plant performance, plant defenses, plant-insect interactions and dynamics within plant communities.
Above-belowground interactions between beneficial microbes, plants, and insects
Ongoing projects: Oriana Sanchez (PhD candidate Jan ‘19)
- During their growing phase, most plants have to deal with attack by insects. Although some do well by chemical defenses alone, many species also recruit help from beneficial microbes in the soil. Interactions with mutualist microbes, which may for instance be various types of rhizobacteria, or mycorrhizal fungi, can in many cases strengthen the plant’s defense response, leading to outcomes similar to those of vaccines in humans. Plants with such beneficial microbes often are more resistant to pests, or pathogens, than plants without these beneficials. Although the concept is known for many years, the exact mechanisms through which this resistance arises are not clear, and it is likely specific to both the plant and microbial species. At the Terrestrial Ecology Group, in collaboration with Dr. Sharon Zytynska at Liverpool University, we study the interactions between a beneficial bacterium extracted from the roots of barley plants, Acidovorax radicis, barley plants, and colonization by aphids. These bacteria have growth-promoting properties in several barley cultivars, and lead to a higher resistance against cereal aphids, Sitobion avenae in most cultivars. Our work aims at unravelling mechanisms through which the bacteria communicate with the plants, and understanding how these interactions operate in a changing world.
Intraspecific phytochemical diversity
Ongoing projects: Lina Ojeda (PhD candidate May ‘21), Annika Neuhaus (PhD candidate Nov ‘21), Robin Heinen.
Although most plants use ‘roughly’ the same chemical machinery to make them function wherever they grow (i.e., primary metabolism), many plants are extremely diverse in their secondary (defense) chemical composition. Obviously, there is a huge variation between species in what chemicals can be found in tissues. However, in the past years, it has become quite evident that there is tremendous variation in secondary metabolism within species. Work at the Terrestrial Ecology Group and elsewhere has revealed strong effects of differences in phytochemical profiles on insects, such as plant colonization by aphids, attendance by ants, and attraction of natural enemies. Our group is involved in the DFG FOR3000 research unit, in which we specifically focus on the effects of intraspecific phytochemical diversity on the assembly of insect communities. Our main model system for this work is Tansy (Tanacetum vulgare), an aromatic plant that shows extraordinary variation in their terpenoid profiles.
Ecological side effects of agricultural pesticides
Ongoing projects: Stephan Grassl (PhD candidate May ‘21)
Industrial agriculture in its current form uses many different forms of pesticides to ensure a healthy crop with a maximized yield. Among these commercial products there are fungicides, herbicides and insecticides, to name a few. Although most products are marketed as environmentally safe, with limited unwanted side effects, a much more likely description would be ‘we have no idea of the full scope of side effects’ for most of them. It is likely that many pesticides have undesirable side effects, for instance on the protective plant microbiome, and via this, likely influence associated pests. At the Terrestrial Ecology Group, we investigate the impacts that fungicides in particular have, on the pathogens they are intended to suppress, on the plant-associated microbiome, and ultimately on interactions with insect pests.
Soil legacy effects
Ongoing projects: Robin Heinen
This part of the theme is a legacy effect in and of itself. This line of work originated during Robin Heinen’s PhD project – studying soil legacy effects on plants and insects – at the Netherlands Institute of Ecology. Soil legacies are changes, either abiotic or biotic, in the soil wrought by plants. Plant species drive soil conditions in different directions. Through this they may influence plants that grow later in the same soil (i.e., plant-soil feedback), or anything that interacts with these plants (e.g., insects). The term ‘soil legacy effects’ is an umbrella term that includes any form of memory that persists in the soil and affects subsequent organisms.