The Becks group studies eco-evolutionary processes that contribute to the maintenance and generation of biodiversity.
Host-parasite coevolution
Coevolution between host and parasites can be an important driver of diversity within and across species, but when and through which processes coevolution removes or favors diversity is still not fully understood. We study host-parasite coevolution using eukaryotic hosts and their viruses. Much of our work examines coevolution between an algal host and its double-stranded DNA viruses, and we use these systems to study coevolutionary patterns (Frickel et al. 2016) and to determine under what conditions the patterns change and how. This includes additional biotic interactions (e.g. host-virus coevolution in the presence of a predator (Frickel et al. 2017) or mutualist (Horas & Becks in prep.) and changes in the abiotic environment (Lohbeck et al. in prep; Theodosiou et al. 2019). Taking advantage of the high experimental tractability of this system (Lievens et al. 2022, 2023), we also study trait variation in chloroviruses of isolates from different locations around the world and from experimental evolutionary studies (Lievens et al. 2024), and the underlying genetic make-up of these changes (Retel et al. 2019, Lievens et al. 2024). Because coevolution between host and virus has strong fitness effects, e.g. the host becomes resistant to viral infection or the virus evolves to overcome resistance, evolutionary changes have strong consequences for population dynamics, while evolutionary changes are at the same time driven by changes in population dynamics (Retel et al. 2022). The overlap of ecological and evolutionary timescales (i.e. eco-evolutionary dynamics) results in distinct population dynamics and patterns at the genomic level (LePennec et al. 2024).
Main collaborators: Philine Feulner, James Van Etten, Dave Dunigan, Irina Agarkova
Funding: German Reserach Foundation (DFG)
As part of our work on coevolution, we also study how viruses of viruses, the virophages, (co)evolve and affect the coevolution of the host and the virus. Working with one of the few trackable experimental systems currently available for working in the laboratory (del Arco et al. 2022), we study the evolution of traits in virus and virophage that determine their level of exploitation and reproduction and how they affect the persistence and the population sizes of host, virus and virophages (del Arco et al. 2024, del Arco & Becks).
Main collaborators: Matthias Fischer
Funding: German Reserach Foundation (DFG) to Ana del Arco, Gordon and Betty Moore Foundation
Evolution of endosymbiosis
Endosymbiosis, where one organism lives inside another, has evolved independently several times, but the conditions that favor this evolutionary transition, and the underlying mechanisms remain elusive. We use a combination of experimental evolution and comparative genomics together to identify the conditions and processes that may favor the evolution of endosymbiosis. Using several ciliate and algal strains that differ in their lifestyle as either facultatively endosymbiotic or obligately free-living, we experimentally test the general hypothesis that conditions that lead to a net positive effect for both partners when living in endosymbiosis, but a net negative effect when living free-living, can lead to the evolution of stable endosymbiosis. Conditions that deviate from this are predicted to lead to destabilization of the endosymbiosis. As part of this work, we identified an important cost of free-living algal partners, namely that endosymbiotic algae are less likely to be eaten than their free-living counterparts (Horas et al., 2016). This condition is important because it suggests that the initial interaction between the ciliate host and the algae, prior to the development of endosymbiosis, is a predator-prey interaction. We explore several aspects of this transition, including cell biological processes, genomic changes in the ciliate and the algal species, and how costs and benefits of the interaction change with the environmental conditions. We are looking for a postdoc working on the theory of this.
Funding: Gordon and Betty Moore Foundation
Mechanisms of coexistence and community dynamics
The functioning of ecological communities is central to life on this planet. We use experiments, modelling, and recently added field work to study the evolutionary and ecological processes and mechanisms that determine coexistence and community dynamics.
An important problem in biology is to identify the determinants of community assembly, the process that shapes the identity and abundance of species within communities over time. To gain a mechanistic understanding of community assembly, we use phytoplankton species in experiments to determine resource use and requirements, for example to predict community assembly of randomly combined species (Zhang & Becks). As the traits underlying resource competition can evolve, we test their role using experimental evolution and aim to integrate them into general rules for community assembly. Using a trait-based approach, we are working with the same phytoplankton species to investigate when and through what processes the distribution of traits within communities determines community dynamics (Vu & Becks). In collaboration with colleagues from Germany and Denmark, we have started a project to apply these techniques and knowledge to predict the consequences of global change in Greenland's waters.
The observation that the timescales of ecological and evolutionary processes can converge requires that we consider the interplay of ecological and evolutionary processes. These eco-evolutionary dynamics become even more important when communities need to keep pace with rapidly changing environmental conditions, as both ecological (i.e. species sorting) and evolutionary processes (i.e. shifts in heritable traits and their underlying genetic make-up) can contribute to community responses. Our research is motivated by the importance of understanding the conditions under which ecological and/or evolutionary processes can contribute. To this end, we study plankton and microbial communities to quantify the relative importance of ecological and evolutionary processes over time (Hermann et al. in press; Pantel & Becks 2023).
To directly test how eco-evolutionary dynamics can contribute to population persistence, we use zoo- and phytoplankton in combination with analyses of model simulations to uncover how evolution in one species can rescue or benefit interacting species that are negatively affected by an environmental stressor (e.g. indirect evolutionary rescue; Hermann & Becks 2022; Réveillon & Becks). An important research question we focus on is how evolution in large communities compares to evolution in single or two-species systems when one or both species evolve . For this we use experimental evolution in multi-species communities in microcosms and mesocosms . Furthermore, we compare trait and genotypic variation across seasons in phytoplankton from Lake Constance (Cristini et al.) and from resurrected phytoplankton from sediment cores and relate these changes to fitness proxies to infer how evolution contributes to changes in population size and response to environmental changes (e.g. re-oligotrophication of Lake Constance).
As part of this work, we implement machine learning tools (Hermann & Becks 2024, Zhang & Becks) and high throughput methods that allows us to quantify abundances of different species and genotypes in mixed cultures.
Main collaborators: Ursula Gaedke, Teppo Hiltunen, Ole Johannsen,Ville Mustonen, Jelena Pantel
Funding: German Reserach Foundation (DFG) to Zhijie Zhang, German Reserach Foundation (DFG), Gips-Schüle Stiftung, BMBF
Intra-genotypic variation and species interactions
Species interactions are at the core of evolutionary biology and ecology. Both fields assume that the outcome of species interactions is based on a fixed trait-fitness relationship. Knowing the fitness-trait relationships, the rate and direction of evolutionary change for these interacting populations can be predicted. Studies using genetically uniform populations or inbred lines growing under the same environmental conditions have revealed substantial phenotypic variation. As this intra-genotypic variation decouples phenotype from genetic and environmental control, predictions of evolutionary change in interacting species become more complex. We will study this using single cell approaches and modelling. We are looking for postdocs to join us on this project.
Funding: Volkswagen Stiftung Momentum Grant