Allometric models of spatial meta-community food webs

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This project will address the interplay of complex spatial and trophic networks. Trophic networks are composed of species that are linked by their feeding interactions in local habitats. Spatial networks comprise local habitat as patches of a non-continuous landscape. These patches are linked by the inter-patch dispersal of the species. The abundance and survival of a species depend on the feeding interactions within the local patches as well as on the dispersal between patches. On the one hand, the structure of the spatial network of patches has effects on the local population densities and eventually the trophic network of species interactions. On the other hand, the structure of the trophic network affects local population densities and survival with knock-on effects on dispersal rates and the spatial network of connected habitat patches. The proposed project will have three major work packages addressing (1) empirical patterns in natural ecosystems, (2) spatial network effects on trophic networks and (3) vice versa. The empirical analyses will address (1) the relationships between body masses and dispersal distances (i.e., quantitative descriptions that large species can bridge larger distances), (2) the structure of natural networks of habitat patches (satellite image analyses how habitat patches are distributed across landscapes), and (3) the turnover of complex trophic networks across space. We will employ these empirical patterns in the theoretical parts of our proposed project and also continue to make them available for the other projects of this research unit. The model analyses of our project will be based on systems of ordinary differential equations (ODE) describing intra-patch (e.g., biomass production, trophic interactions) and inter-patch processes (dispersal). Integration of these ODEs will yield time series of species biomass densities that will be analysed for persistence (survival), population stability (e.g., coefficient of variation in biomass densities), and the local (on patches) and global (integrated across all patches) trophic network structures. We will address two main questions: (1) how does the structure of the spatial network and patch heterogeneity in terms of linkedness as well as abiotic variables affect the persistence stability and structure of the trophic networks; (2) how do trophic interactions among species and between species and the abiotic environment shape the emergent spatial network and the resulting spatial variability in the trophic network?