Slime mould imitates transport networks in China

Purpose - The purpose of this paper is to study the slime mould Physarum polycephalum as an ideal biological substrate for transport networks. When presented with several sources of nutrients the slime mould propagates colonises the sources and spans them with a network of protoplasmic tubes allegedly optimised for transfer of nutrients and metabolites. Such formation of slime mould's protoplasmic network resembles development of man-made transport systems. Thus, it sounds reasonable to compare the protoplasmic network with an established network of vehicular transport links to uncover potential (dis-)similarities between slime mould grown and man-made networks and shed more light onto general principle guiding growing biological and socio-engineering systems. Design/methodology/approach - The paper proceeds by representing major urban areas of China by oat flakes, inoculating the slime mould in Beijing, waiting till the slime mould colonises all urban areas, or colonises some and cease further propagation, and analysing the protoplasmic networks formed and comparing with man-made motorway network and planar proximity graphs. Findings - Laboratory experiments found that P. polycephalum provides a very good match for the Chinese motorway networks. Moreover, both the Chinese motorway network and the slime mould protoplasmic networks have minimum spanning trees and other proximity graphs as their sub-graphs. The experiments also identified the urban areas unlikely to be spanned by the protoplasmic networks, which may reflect hot-spots in existing challenges of modernising the motorways. Originality/value - The paper demonstrated the strong component of transport system built by slime mould of P. polycephalum on major urban areas of China consisting of one chain of four nodes and one planar graph with three leaves and eight cycles; the planar graph resides on the urban areas in the south-east part of China.