Structure, stability and functioning of food webs

1. Effects of temporal variability of spatial networks on meta-community food-web stability and diversity

This project investigates the structure and stability of complex food webs on a spatial network of habitat patches. We focus on temporal variability of the spatial network structure and its effects on biodiversity and population stability on local and regional scales. The spatial networks consist of isolated habitat patches that are embedded in a landscape. The links of the spatial networks are created by the species' abilities to disperse between habitat patches over varying distances. The availability of patches as habitat for a local community as well as the accessibility of dispersal routes changes over time, thereby changing the structure of the spatial networks.

In this project, computer-generated trophic and spatial networks are analysed. The population dynamics of the species are simulated with mathematical models based on ordinary differential equations. The survival of a species in a certain habitat depends on the availability of resources and the mortality through predation (and thus on the composition of the local community). Furthermore, its survival on the regional level depends on the ability to disperse over the landscape and colonise suitable habitat patches. We address different aspect of temporal variability of spatial networks, e.g. periodically blinking links (dispersal routes), not permanently available patches or variable environmental conditions.

This project is part of the DFG research group "Networks on Networks: The interplay of structure and dynamics in spatial ecological networks". Collaboration partners: Barbara Drossel, Ulrich Brose, Björn Rall, Bernd Blasius, Thilo Gross.

2. Dynamics of stage-structured populations

Classical mathematical models of population dynamics depend on equations that include terms for predation, reproduction and mortality. However, they usually neglect that biological individuals have a life cycle and that ontogenetic development and growth are necessary requirement for reproduction. We analyse with theoretical methods (computer simulations and analytical calculations) how the ontogenetic structure of populations affects the dynamics and the stability of small modules of interacting species or of complex food webs.