Georg Everwand, Dr. Christoph Scherber, Prof. Dr. Teja Tscharntke

The relative importance of grassland management and plant diversity for plant-herbivore-predator and plant-pollinator interactions

This project focuses on plant-invertebrate interactions in grasslands along gradients in management intensity.
We study the functional responses of grassland invertebrates to fertilization and mowing frequency. Selective herbicide use allows analyzing the relative role of herbs and grasses for responses to management practices, including changes in insect community structure and ecosystem functioning. Experimental approaches (such as the exposure of phytometers, sweep netting and pan trapping) are used to study the functional consequences (mediated by invertebrates) of different management practices.

Hella Schlinkert, Dr. Catrin Westphal, Dr. Carsten Thies, Prof. Dr. Teja Tscharntke

Multitrophic interactions along a plant-size gradient in Brassicaceae

Global species richness is estimated to be up to 100 million species. Many of these species interact with each other. Interactions, whether intra- or interspecific, define a large part of ecosystem functioning. Interspecific interactions among plants and insects are common. These interactions can either be beneficial or detrimental. Mutualistic relationships between plants and their pollinators or between plants and the natural enemies of their herbivores are beneficial for both interacting species. Antagonistic interactions for instance between plants and herbivores have negative effects on one or even both partners. Nevertheless we still do not know which general patterns of interactions exist, and which are the underlying mechanisms. However, the knowledge of such general patterns and mechanisms is important to make accurate predictions, for example in applied practice of biological control or conservation of biodiversity.
The study will analyse whether plant size and the size of plant compartments like flowers or leaves are a predictor for changes in the diversity and community patterns of pollinators, herbivores and their natural enemies. In addition, possible interactions between mutualistic and antagonistic species (e.g. pollinators and herbivores) will be investigated along the plant size gradient.
To test plant size as a predictor for changes in the diversity and community patterns of different functional groups of insects and their importance for plants, we established a plant-size gradient in a common garden experiment: We established 100 plots using 25 Brassicaceae species differing in size. On these plots we will assess diversity and community structure of pollinators, ecto- and endophagous herbivores, predators, parasitoids and ectophytic fungi along a plant-size gradient. Furthermore we will assess seed set of open pollinated and wind pollinated plant individuals, feeding damage and concentration of glucosinolates as an indicator of induced defence.