Trophic interactions between microcrustacean zooplankton and phytoplankton in two temperate reservoirs: reanalysis of dietary data using bipartite graph and network analysis

Bipartite graph is a graph in which the vertex set of the graph can be partitioned into two non-empty subsets. Each edge of the graph has one end in one subset and the other end in another subset. In ecological applications of the bipartite graph for food webs, one subset of the vertices consists of predator species and another subset of the vertices consists of prey species. Each edge connecting between two subsets of the vertices depict two-level food webs. Such food webs are amenable to network analysis to understand their structure and likely functioning. In this study, available dietary data for microcrustacean zooplankton of two reservoirs in southeast Australia were reanalysed using bipartite graph and network analysis. For each reservoir, an entire web with interaction strengths was effectively visualised by bipartite graph. Modularity (or link-rich clusters of species) of the web was also visualised with the partitioning of the reservoir zooplankton species into distinct groups based on their dietary phytoplankton. Although the application of bipartite graph and network analysis are limited to two-level food webs, they offer insightful analytical tools for aquatic food webs.