Research Projects

We analyse ecological systems as different types of networks, including trophic networks of predator-prey interactions and spatial networks of habitat patches. These research areas are linked by the general use of allometric scaling functions that relate network parameters such as feeding strength or movement rates to the body masses of the species.

Our research is organised under the following overarching research topics

Predator-prey interactions and trophic networks

In this research field, we address how species’ body masses and environmental variables such as temperature affect predator-prey interactions and the complex trophic networks of natural communities.

more on predator-prey interactions and trophic networks

The earth’s ecosystems comprise millions of species that are engaged in billions of interactions. The organisation (who is feeding on whom) and the strength of these feeding interactions are critically important for community stability and maintaining biodiversity. However, the enormous number of interactions renders systematic empirical measurements of their strengths impossible, thus limiting our ability to understand the structure, dynamics, and stability of natural trophic networks.

How can we obtain a generalized and predictive understanding of interactions between species?

Our primary approach to understanding predator-prey interaction strengths is to focus on constraints by their body masses. We found systematic effects of body masses on feeding rates and functional response parameters (Rall et al. 2012, Kalinkat et al. 2013). The resulting non-random distributions of interaction strengths across species pairs yield a high system stability (Heckmann et al. 2012). Together, these findings show how body masses determine the structure, dynamics and stability of trophic networks in nature. Our current research comprises constraints on species-coexistence patterns in microbial networks, effects of space (habitat size) on interaction strengths and population dynamics and forecasting ecological dynamics.

What are the consequences of climate warming for species’ interactions and trophic networks?

In systematic laboratory experiments, we analysed the increase in consumer feeding rates relative to their metabolism (Vucic-Pestic et al. 2011, Lang et al. 2012). In contrast to prior expectations, we found that the relatively weaker increase in feeding rates stabilises population oscillations at the risk of consumer starvation (Fussmann et al. 2014). Surprisingly, these destabilising warming effects can be buffered by nutrient enrichment (Binzer et al. 2016). In ongoing research projects, we address how global change affects interaction strengths and ecosystem functioning.

Binzer, A. et al. 2016. Interactive effects of warming, eutrophication and size structure: impacts on biodiversity and food-web structure. – Glob. Change Biol. 22: 220–227.

Fussmann, K. E. et al. 2014. Ecological stability in response to warming. – Nat. Clim. Change 4: 206–210.

Heckmann, L. et al. 2012. Interactive effects of body-size structure and adaptive foraging on food-web stability. – Ecol. Lett. 15: 243–250.

Kalinkat, G. et al. 2013. Body masses, functional responses and predator–prey stability. – Ecol. Lett. 16: 1126–1134.

Lang, B. et al. 2012. Warming effects on consumption and intraspecific interference competition depend on predator metabolism. – J. Anim. Ecol. 81: 516–523.

Rall, B. C. et al. 2012. Universal temperature and body-mass scaling of feeding rates. – Philos. Trans. R. Soc. B Biol. Sci. 367: 2923–2934.

Vucic-Pestic, O. et al. 2011. Warming up the system: higher predator feeding rates but lower energetic efficiencies. – Glob. Change Biol. 17: 1301–1310.

Movement, meta-communities and spatial networks

In this research field, we study (1) how species traits such as body mass and movement mode affect movement patterns, (2) what determines the stability of metacommunities and (3) how species’ movement creates spatial networks of habitat patches.

more on movement, meta-communities and spatial networks

Experimental metacommunities and microbial networks

In this research field, we test the predictions of ecological network theory in microbial microcosms of bacteria and their protist consumers.

more on experimental meta-communities and microbial networks

A big challenge in ecology is to link theory predictions obtained under simplifying assumptions to the complex patterns and processes found in natural ecosystems. For instance, natural communities are not only characterized by an entangled structure of inter- and intraspecific interactions between species but also by heterogeneous spatial distributions of habitat patches linked by species dispersal. The structure of these trophic and spatial networks constrains the diversity, dynamics and functioning of the communities. Therefore, experimental systems need to establish these types of networks under controlled and replicable conditions.

How can microbial networks help us to understand theory predictions?

Microbial networks comprising protists and bacteria have a long history in ecology. They have the big advantage that they are easy to manipulate, highly flexible and represent a great tool to test theoretical predictions in relatively short time. For example, it was generally assumed that global warming destabilizes natural systems due to an increased speed of life and accelerated oscillations. However, our microcosm experiments revealed that predator-prey (protozoa-bacteria) interactions are stabilized by warming due to dampened oscillations in population cycles, whereas extinctions due to predator starvation become more likely (Fussmann et al. 2014). Our current research investigates the processes driving coexistence in microbial networks comprising protists and bacteria on sugar resources.

Fussmann, K. E. et al. 2014. Ecological stability in response to warming. – Nat. Clim. Change 4: 206–210.