Trying to summarize my research with a few key words, ecological networks, specialization, temporal dynamics and (insect) biodiversity might do. My research interests are based on my fascination for nature and biodiversity. I am puzzled by how many different species (especially insects) can be found on our planet and how many stories can be told when you look at them closely. In my view, fundamental research that keeps in mind the current environmental challenges is the way we can move towards a better understanding of nature, which will prove useful for a sustainable future (but has also merits in its on right). That being said, I am also involved in and open to collaborations that are already trying to implement current understanding and novel approaches into applications for nature conservation or ecosystem (forest, agricultural) management.
I try my best to integrate observation, experimentation and theory to achieve this, mostly asking questions about species communities, interspecific interactions and environmental change. One theme is to identify mechanistic predictors of dynamics and variation in biotic niches and interaction patterns on different scales. I search for ecological conclusions that give sense in light of both theory and natural history, and that are unlikely to be caused by sampling artifacts.
My research (past and ongoing) can be loosely grouped into three focal areas: 1) mutualistic interactions (with a special focus on plant-pollinator interactions), 2) antagonistic interactions (with a special focus on tree-herbivore interactions) and 3) modeling and analyzing species interaction networks. In all three cases, I am particularly interested in understanding the importance of biodiversity and timing / temporal dynamics for interaction outcomes (population dynamics and ecosystem functioning). Of course, these three themes are closely connected.
Much of my work so far deals with plant-pollinator interactions in a community context, but I am also studying other mutualistic (seed dispersal) and antagonistic (plant-herbivore, host-parasitoid, predation) interactions. I have specific experience with various plants and a wide range of animals, including bees, wasps, ants, dragonflies and damselflies, birds, neotropical bats, aphids, caterpillars and their parasitoids, weevils and bark beetles.
Main Themes (selection of ongoing research)
Understanding, modeling and predicting temporal network dynamics with a focus on plant-pollinator networks
Ecological network analysis has often focused on analyzing aggregated and isolated datasets. In our work, we are trying to go beyond analyzing single network matrices, and understand the spatio-temporal dynamics of interactions (in particular so called “network rewiring”), connecting different networks by species identity. I am trying to develop empirical and theoretical approaches in parallel, synthesizing current knowledge and trying to marry models and data. Fitting mechanistic network models to real, imperfect data will improve both, theoretical understanding and analysis of empirical patterns.
With my PhD student Benjamin Schwarz, who was funded by a recent DFG project, I focused on the temporal dimension of network ecology, with a focus on plant-pollinator networks. We looked at temporal dynamics on multiple timescales (within a day, within a year and among years). This work is being continued in further projects.
Currently, I am concentrating more on the modeling side of it, together with people from the REASSEMBLY research unit, including PhD student William Castillo. We are further developing our tools to predict interaction networks for novel communities.
Other collaborators for this topic include Diego Vázquez, Carsten Dormann, Gita Benadi and Christopher Kaiser-Bunbury.
Tree species diversity effects and insect-mediated interactions between neighbor trees
I am trying to understand the network of interactions around herbivorous insects on trees. Thispart of my research work is currently concentrated on collaborations within the TreeDivNet tree diversity experiments.
As a collaboration within the IDENT network, we are developing tree-herbivore-enemy networks for a set of tree diversity experiments in Europe and North America. I want to use the temporal networks approach to help explain variation in tree diversity effects on herbivory and understand how exotic trees are integrated into native tree-herbivore networks. PhD student Sylvie Berthelot (funded by Baden-Württemberg-Stiftung, Eliteprogramm for Postdocs) has been working on this project and done comparisons between different IDENT sites, which provide a unique test of the hypothesis that exotic species are less attacked by herbivores than native species. In IDENT-Freiburg, I am looking at tree diversity effects on herbivores since 2016 with a changing team of students.
Main collaborators in this line of research include Michael Scherer-Lorenzen, Jürgen Bauhus, Charles Nock, Christian Messier, Alain Paquette, Dominique Gravel and many others of the TreeDivNet network.
Jochen Fründ 