PD Dr. Christian Guill
Research Topics
Metacommunity Ecology
Metacommunities are sets of local ecological communities that are linked by the dispersal of multiple interacting species (Leibold et al., Ecol. Lett. 2004). They provide a powerful framework to study drivers of biodiversity and ecosystem functioning by accounting for dynamics on multiple spatial scales: within local communities, populations of different species interact as they compete for shared resources or because they are in a predator-prey relationship, while populations of the same species on different habitat patches interact via the exchange of individuals (dispersal). These different interaction types affect each other because they are commonly density-dependent, i.e., their strength depends on the abundance of conspecifics and other species.
Structure, stability and functioning of food webs
Food webs are the networks of predator-prey interactions in an ecological community. As such, they govern the distribution of resources all organisms need to survive and are therefore critical for understanding the persistence and diversity of species in an ecosystem. Using numerical simulations of large, complex food webs with 100+ species, I address how energetic traits of the species affect the biomass structure (bottom-heavy or top heavy) of food webs, how this in turn affects the stability against perturbations caused by global change, or how adaptability of traits determining the interactions between predator and prey species affect their coexistence.
PD Dr. Christian Guill
Campus Botanischer Garten
University of Potsdam
Ecology and Ecosystem Modelling
Maulbeeralle 2, building 2, room 2.02
14469 Potsdam
Specific projects
Selforganisation in metacommunities
An important driver of biodiversity in metacommunities is habitat heterogeneity. Different abiotic or biotic environmental conditions on different habitat patches provide niches for various species, which enhances diversity on the regional (metacommunity) level and via source-sink dynamics also on the level of local communities. This habitat heterogeneity can be created by external factors (e.g., different soil quality or resource availability among the patches). However, due to the interplay of the dynamical processes on the local and on the regional scale, habitat heterogeneity can also emerge in a process called self-organised pattern formation. The phenomenon occurs in different ecological systems but is perhaps best known from vegetation patterns in arid ecosystems (Meron, Nonlinear Physics of Ecosystems, 2015). In spatially discrete systems like metacommunities that are a priorily patchy, the patterns take for form of abundance differences of the species among the patches.
Maintenance of functional diversity by self-organised pattern formation
Using a small model food web oriented at phyto- and zooplankton communities in lakes we investigate how locally different selection pressures and source-sink dynamics created by self-organised pattern formation affect the maintenance of functional diversity of the phytoplankton within and among local communities. Harnessing the power of modern trait-based approaches, diversity within the phytoplankton communities is described by a continuous distribution of a functional trait that affects the defence against zooplankton grazers and trades off with the maximum growth rate or the ability to take up nutrients at low concentrations. We are interested in the effect of drivers on multiple organisational levels, from the size and complexity of the patch network over the diversity of the zooplankton predators to the shape of the trade-off between defence and growth rate in the phytoplankton community. The topic thus combines metacommunity ecology, trait-based ecology, and eco-evolutionary dynamics. The analyses are lead by my PhD student Louica Philipp.
Potential topics for Master- and Bachelor-Theses
The size of the patch network of a metacommunity (i.e., the number of habitat patches) and its complexity (i.e., the number of dispersal links per patch) determines whether self-organised pattern formation occurs and, if so, how strong the mergent patterns are (i.e., how much the abundances of the species differ among the patches). The relationship between the properties of the habitat network and the strength of pattern formation is ecologically relevant for the maintenance of diversity, but it is not well understood. The goal of a Bachelor- or Master-project in this context would be to establish how the connectance of the patch network, distance-dependent dispersal rates, or species-specific dispersal networks affect the strength of the mergent patterns and thus the basis for maintenance of diversity.
Eco-evolutionary dynamics in metacommunities
We have recently shown that emergent habitat heterogeneity due to self-organised pattern formation allows consumers with a single shared resource to coexist in metacommunities where an equivalent amount of externally determined habitat heterogeneity would not [link to study]. This is based on a feedback loop between competing species that differ in their abilities to induce pattern formation and to benefit from it. It also implies that dispersal-related traits (like maximum dispersal rate or sensitivity to dispersal-inducing cues) are under evolutionary selection, which can in the long term affect the ability of a community to exhibit pattern formation. First results based on a simplified version of the planktonic system described above indicate that dispersal traits tend to evolve such that the emergent patterns weaken or pattern formation is prevented altogether. However, this depends on the size and complexity of both the patch network and the local communities, as also sudden switches between qualitatively different patterned states are possible.
Potential topics for Master- and Bachelor-Theses
The conditions under which self-organised pattern formation consistently occurs under the evolution of dispersal traits of the relevant species are not well established. The goal of a Bachelor- or Master-project in this context would be to conduct an evolutionary invasion analysis based either on the simplified planktonic system in metacommunities of varying size and complexity or on more complex ecological systems (e.g., a food chain that includes an additional top predator) in two-patch metacommunities. Thereby, such a project would combine classical ecological interactions, dispersal dynamics, and evolutionary dynamics.
Experimental verification of self-organised pattern formation in planktonic metacommunities
Lead: Dr. Toni Klauschies. Self-organised pattern formation is known from a variety of ecosystems, like mussel beds, benthic diatoms, dryland vegetation, or subarctic shrubs and trees (Rietkerk and van de Koppel, Trends Ecol. Evol. 2008). These systems have in common that space itself is continuous and roughly homogeneous, which leads to very conspicuous patterns in the form of spots, stripes, or labyrinth shapes. In network-organised systems like metacommunities, where the habitable space itself consists of discrete patches, self-organised pattern formation has been theoretically predicted, but because the emergent patterns are far less conspicuous, empirical or experimental evidence is rare. We develop experimental metacommunities consisting of different algae and zooplankton species (e.g. rotifers) with continuous or semi-continuous nutrient turnover. A technical challenge is to manipulate the connections between the habitat patches such that the diffusion- or dispersal rates of nutrients, algae, and rotifers are sufficiently different from each other, as this is a prerequisite of pattern formation.
Potential topics for Master- and Bachelor-Theses
To complement the experimental work in the laboratory and to gain better mechanistic understanding of the observed patterns, a project on this topic would aim at simulating a small food web that is similar to the experimental community. In contrast to the communities considered so far, this would involve a combination of algae swimming freely and algae in biofilms, as well as zooplankton grazers that specialise on either of the algae.
Biomass structure of food webs and their stability against perturbations
Natural food webs often have a bottom-heavy biomass distribution, but in some cases also top-heavy biomass distributions are found. We are interested in how this is related to energetic traits of the species (e.g., their activity respiration vs. their resting respiration). We furthermore investigate how the resulting biomass structure affects a food web's response to press perturbations (long-lasting alterations of species' abundances or their growth rates, caused e.g. by effects related to global change) and how well this response can be predicted by species' traits (in collaboration with Xiaoxiao Li).
Trait adaptability and the stability of food webs
In collaboration with my colleague Dr. Ellen van Velzen I investigate how adaptability of traits related to defensive or offensive capabilities of prey and predator species affects the persistence of species and the functioning of the entire community (e.g. in terms of biomass production or community respiration rate). Using tri-trophic food webs with idealised structure, we have already shown that functional diversity, especially at the level of the top predators, enables adaptive and compensatory dynamics throughout the food web that ultimately allows for efficient biomass transfer along the food chains (study 1, study 2). However, it is unclear how these and related effects like evolutionary rescue by trait adaptation transfer to large, complex food webs with realistic structure.
Scientific Career
since 2015 Senior Scientist, Institute for Biochemistry and Biology, University of Potsdam
2013 - 2015 Postdoc, Institute for Biodiversity and Ecosystem Dynamics, Universiteit van Amsterdam, NL
2010 - 2013 Research Assistant, J.-F.-Blumenbach-Institute for Zoology and Anthropology, Georg-August-University Göttingen, Germany
2010 PhD in Theoretical Physics, Technical University of Darmstadt, Germany
2007 - 2010 Research Assistant, Institute for Solid State Physics, Darmstadt University of Technology
2007 Diploma in Physics, Darmstadt University of Technology
Publications
Gaedke, U., Li, X., Guill, C., Hemerik, L. & de Ruiter, P. (under review) Seasonal shifts in trophic interaction strength drive stability of natural food webs. Resubmitted to Ecol. Lett., preprint doi: 10.22541/au.172535913.30167932/v1
Guill, C.*, Nößler, F.* (shared first authorship) & Klauschies, T. (2024) Self-organised pattern formation promotes consumer coexistence by fluctuation-dependent mechanisms. Funct. Ecol., https://doi.org/10.1111/1365-2435.14663.
Wojcik, L.A., Klauschies, T., van Velzen, E., Guill, C. & Gaedke, U. (2024) Integrating different facets of diversity into food web models: how adaptation among and within functional groups shape ecosystem functioning. Oikos e10544, https://doi.org/10.1111/oik.10544.
Acevedo-Trejos, E., (...), Guill, C., (...), Prowe, F. (17 authors total) (2022) Modelling approaches for capturing plankton diversity (MODIV), their societal applications and data needs. Front. Mar. Sci., https://doi.org/10.3389/fmars.2022.975414.
Guill, C.*, Hülsemann, J.* (shared first authorship) & Klauschies, T. (2021) Self-organized pattern formation increases functional diversity. Ecol. Lett., https://doi.org/10.1111/ele.13880.
Stark, M., Bach, M. & Guill, C. (2021) Patch isolation and periodic environmental disturbances have idiosyncratic effects on local and regional population variability in meta-food chains. Theor. Ecol., doi: 10.1007/s12080-021-00510-0.
Ceulemans, R., Guill, C. & Gaedke, U. (2021) Top predators govern multitrophic diversity effects in tritrophic food webs. Ecology 102, e03379.
Gross, T., Allhoff, K.T., Blasius, B., Brose, U., Drossel, B., Fahimipour, A.K., Guill, C., Yeakel, J.D. & Zeng, F. (2020) Modern models of trophic meta-communities. Phil. Trans. R. Soc. B 375, 20190455.
Ceulemans, R., Gaedke, U., Klauschies, T. & Guill, C. (2019) The effects of functional diversity on biomass production, variability, and resilience of ecosystem functions in a tritrophic system. Sci. Rep. 9, 7541.
Miele, V., Guill, C., Ramos-Jiliberto, R. & Kéfi, S. (2019) Non-trophic interactions strengthen the diversity-functioning relationship in an ecological bioenergetic network model. PLoS Comput. Biol.15(8): e1007269.
Ryser, R., Häussler, J., Stark, M., Brose, U., Rall, B.C. & Guill, C. (2019). The biggest losers: habitat isolation deconstructs complex food webs from top to bottom. Proc. Roy. Soc. Lond. B. 286, 20191177.
Kath, N., Boit, A., Guill, C. & Gaedke, U. (2018) Accounting for activity respiration results in realistic trophic transfer efficiencies in allometric trophic network (ATN) models. Theor. Ecol. 11, 453–463.
Gaedke, U., Beisner, B.E., Binzer, A., Downing, A., Guill, C., Klauschies, T., Kuiper, J.J., Soudijn, F.H & Mooij, W.M. (2017) Importance of trait-related flexibility for food web dynamics and the maintenance of biodiversity. In: Adaptive Food Webs: Stability and Transitions of Real and Model Ecosystems. Cambridge University Press. Editors: John C. Moore, Peter C. de Ruiter, Kevin S. McCann, Volkmar Wolters.
Nilsson, K.A., Caskenette, A.L., Guill, C., Hartvig, M. & Soudijn, F.H. (2017) Including the life cycle in food webs. In: Adaptive Food Webs: Stability and Transitions of Real and Model Ecosystems. Cambridge University Press. Editors: John C. Moore, Peter C. de Ruiter, Kevin S. McCann, Volkmar Wolters.
Schneider, F.D., Brose, U., Rall, B.C. & Guill, C. (2016) Animal diversity and ecosystem functioning in dynamic food webs. Nature Communications 7, 12718.
Binzer, A., Guill, C., Rall, B.C. & Brose, U. (2015) Interactive effects of warming, eutrophication and size-structure: impacts on biodiversity and food-web structure. Global Change Biol. 22, 220-227.
Guill, C. & Paulau, P. (2015) Prohibition rules for 3-node substructures in ordered food webs with cannibalistic species. Israel J. Ecol. Evol. 61, 69-76.
Allhoff, K.T., Ritterskamp, D., Rall, B.C., Drossel, B. & Guill, C. (2015) Evolutionary food web model based on body masses gives realistic networks with permanent species turnover. Sci. Rep. 5, 10955.
Pfaff, T., Brechtel, A., Drossel, B. & Guill, C. (2014) Single generation cycles and delayed feedback cycles are not separate phenomena. Theor. Pop. Biol. 98, 38–47.
Schmitt, C.K., Guill, C., Carmack, E. & Drossel, B. (2014) Effect of introducing a competitor on cyclic dominance of sockeye salmon. J. Theor. Biol. 360, 13–20.
Guill, C., Carmack, E. & Drossel, B. (2014) Exploring cyclic dominance of sockeye salmon with a predator-prey model. Can. J. Fish. Aquat. Sci. 71, 959–972.
Schmitt, C.K., Schulz, S., Braun, J., Guill, C. & Drossel, B. (2014) The effect of predator limitation on the dynamics of simple food chains. Theor. Ecol. 7, 115–125.
Kalinkat, G., Schneider, F.D., Digel, C., Guill, C., Rall, B.C. & Brose, U. (2013) Body masses, functional responses and predator-prey stability. Ecol. Lett. 16, 1126–1134.
Schmitt, C.K., Guill, C. & Drossel, B. (2012) The robustness of cyclic dominance under random fluctuations. J. Theor. Biol. 308, 79–87.
Binzer, A., Guill, C., Brose, U. & Rall, B.C. (2012) The dynamics of food chains under climate change and nutrient enrichment. Phil. Trans. Royal. Soc. Lond. 367, 2935–2944.
Plitzko, S.J., Drossel, B. & Guill, C. (2012) Complexity-stability relations in generalized food-web models with realistic parameters. J. Theor. Biol. 306, 7–14.
Heckmann, L., Drossel, B., Brose, U. & Guill, C. (2012) Interactive effects of body-size structure and adaptive foraging on food-web stability. Ecol. Lett. 15, 243–250.
Guill, C., Reichhardt, B., Drossel, B. & Just, W. (2011) Coexistence of two periodic attractors: the degenerate Neimark Sacker bifurcation as a generic mechanism. Phys. Rev.E 83, 021910.
Guill, C., Drossel, B., Just, W. & Carmack, E. (2011) A three-species model explaining cyclic dominance of pacific salmon. J.Theor. Biol. 276, 16–21.
Kartascheff, B., Heckmann, L., Drossel, B. & Guill, C. (2010) Why allometric scaling enhances stability in food web models. Theor. Ecol. 3 195–208.
Guill, C. (2010) A model of large-scale evolution of complex food webs. Math. Model. Nat. Phenom. 5, 139–158.
Guill, C. (2011) Dynamik alters- und stadienstrukturierter Populationen. Doctoral thesis, online publication, Darmstadt. tuprints.ulb.tu-darmstadt.de/2411/, Technische Universität Darmstadt.
Kartascheff, B., Guill, C. & Drossel, B. (2009) Positive complexity-stability relations in food web models without foraging adaptation. J. Theor. Biol. 259, 12–23.
Guill, C. (2009) Alternative dynamical states in stage-structured consumer populations. Theor. Pop. Biol. 76, 168–178.
Guill, C. & Drossel, B. (2008) Emergence of complexity in evolving niche-model food webs. J. Theor. Biol. 251, 108–120.
Rall, B., Guill, C. & Brose, U. (2008) Food-web connectance and predator interference dampen the paradox of enrichment. Oikos 117, 202–213.