Food web visualisation: Heat map, interactive graph and animated flow network

Abstract

Abstract Food webs are the physical foundations of ecosystems. Visualisations help to find and present structural patterns of these weighted networks and are essential in research, conservation practice and education. There has been no open‐source library drawing weighted food webs with fractional trophic levels clearly. The existing approaches are scattered across separate libraries and programming languages. We provide an ensemble of mutually complementary visualisation methods that enable a general overview of the system, as well as a clear presentation of its details: https://github.com/ibs‐pan/foodwebviz. We use colours, sizes, positions, zoom and movement for precise identification of flows, their magnitudes and connectivity patterns. Vertical positions of nodes highlight the fractional trophic level as the most significant structural variable in a food web. The visualisations are in the form of modular and extensible python functions. Jupyter notebooks display them interactively in HTML. A heat map of food web flows or diet proportions shows their general pattern at a glance while retaining their precise identification. An interactive graph allows tracing the flow of matter over subsequent links. The user can select nodes, zoom, adjust layout parameters and manually drag‐and‐drop nodes. An intuitive animation of particles moving between the nodes uses colours and time dimension to trace connections better. It shows the multivariate food web aspects in one graph, together with a structural indicator, the trophic level. A bar plot and a heat map summarise exchanges of matter between the trophic levels. We bring several complementary and customisable methods together to facilitate accompanying every food web publication and analysis with its visualisation. Users can tinker with the interactive output and method parameters to reach the desired effect. Aesthetically appealing images presenting empirical data help to communicate the importance of species interconnectedness and ecosystem complexity to the broader public. Visualisation tools facilitate incorporating real‐world examples in education.

Keywords

• food web
• network visualisation
• ecological network
• animated flow network
• interactive graph
• trophic level