Synthesis of spatial and trophic networks and their response to global change

Abstract

Increasing human demands for production and goods continuously leads to the loss and fragmentation of habitat and eutrophication and threatens biodiversity. Organisms that comprise biodiversity interact with each other and depend on each other and thus, biodiversity is organised in complex interaction network. On the one hand, food-web research has addressed how trophic interactions shape local communities and how global change drivers such as eutrophication affects them. On the other hand, metacommunity research has been focused on spatial distributions and geographic drivers of local and regional biodiversity and how global change drivers such as habitat fragmentation species communities. These two realms have, however, mostly been separate. In this thesis, I present a meta-food-web model that synthesizes local trophic interactions and interpatch dispersal. This model employs species body masses as an interlinking trait that creates food webs and trophic dynamics through predator-prey body mass ratios and spatial networks through species dispersal capacities. With the meta-food-web model, I uncover mechanisms shaping biodiversity that only arise as a consequence of the synthesis of spatial and trophic interactions. The perspective from meta-food-webs reveals that the effect of global change drivers such as eutrophication and habitat fragmentation are highly context dependent and their effect depends on food-web and landscape structures. Furthermore, I show that interacting global change drivers can create non-linearities in biodiversity responses. Thus, this thesis provides a tool and theory derived hypotheses to shed light on consequences of global change and on what may be important to conserve biodiversity.