Statistical models for generating and analysing spatial meta-community food-webs

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In this project we aim to further our understanding about the structure and dynamics of meta food-webs. For this effect we will combine data analysis of natural food-webs, numerical simulations in systems of coupled patches, and the development of trophic patch dynamics models, organized in four work packages: (1) Analysis of the spatio-trophic organization in natural meta food-webs. We will develop robust indices to characterize spatial food-web structure, explore the scaling of trophic structure with space, and quantify temporal changes in meta food-webs. The analysis will be based on empirical food-web data sets, but will also be applied to non-trophical ecological interactions, as well as to network-on-networks in other natural systems. Finally, the algorithms will be integrated into an open, publicly-available R-package. (2) Numeric (ODE) simulations in large networks of coupled patches to study the role of spatial inhomogeneities and temporal disturbances for the structure and dynamics in meta-food webs. First, we will investigate the influence of core-satellite range distributions, nested patterns of species distributions on patches, quenched spatial inhomogeneities (e.g., parameter disorder and salient patches), spatial gradients in food-web structure, and the influence of patch size heterogeneity. Second, we will address temporal aspects in meta food-webs. We will study the response to pulse-perturbations, the role of correlated disturbances at different patches to synchronize population dynamics (Moran effect), and the propagation of small fluctuations in the spatial and trophic network. (3) Community assembly of meta food-webs by stochastic, sequential colonization and extinction events. We will numerically study the patch dynamics in spatial explicit models, extending previous research to more realistic, complex dispersal networks. Next, we will develop spatially implicit patch dynamics models that describe the patch density for each species or interaction. Finally, we will extend structural metapopulation models, that incorporate patch size distributions and abundance distributions, for trophic interactions to link metapopulation and population dynamics models. (4) We will use the developed trophic metapopulation framework to study the influence of habitat loss and fragmentation for the structure of meta food-webs, such as the number of trophic levels. We will test whether habitat fragmentation has a strong influence on higher trophic levels and thereby increases the abundance of basal species (positive fragmentation effect), and whether this effect is mitigated by the larger dispersal capabilities of species at higher trophic levels.