Hierarchical networks

Abstract

Biological networks are not operating in isolation, but are connected and interact with the other levels of the entire ecological hierarchy. It implies that both vertical and horizontal connections and interactions come into play and should be considered. The vertical effects and their integration with the horizontal networks are, however, a new challenge, as network theory up to now to a high extent has only considered the horizontal connections. It gives rise to the central questions, how two or more networks in two or more different levels of the hierarchy can work together and whether the interactions will change the network properties.The hierarchical levels in biology and ecology – molecules, cells, organs, organisms, populations, ecosystems, landscapes and the ecosphere – appears at first sight to be working two by two (molecules/cells, cells/organs, organs/organism, organisms/population, populations/ecosystems and landscapes/the ecosphere), with levels like molecules, organs, populations and landscapes forming competing horizontal network, which are driven by an energy input on the cell, organism, ecosystem and ecosphere level, respectively.A network model study of a landscape consisting of a network of ecosystems that are represented by networks – it means networks within a network – has been applied in these investigations to answer the raised questions. The study has shown that the ecosystem, which is able to use the resources with the highest efficiency in the landscape will win. Based on the obtained results from the model experiments it can be hypothesized that a “kind” of Darwinian selection may take place at all the levels of the hierarchy and that the winner is the one which is able under the prevailing conditions to obtain and exploit? most work energy. There are strong supports in the literature (see for instance Jørgensen, 2012) in the case for individuals and populations in ecosystems (formulated in the so called ELT, that have many observable supports; see Jørgensen, 2012). The model experiments presented here point toward an expansion of the ELT to ecosystems competing in the landscape, but a general expansion to all the hierarchical levels in ecology will require many more model experiments and more concrete observations (case studies).