Fig. 1: Network models used in macroevolution.

A, B Standard first-order network representations. A Bipartite occurrence network. This representation comprises two sets of physical nodes that represent geographic areas and taxa²⁵. B Unipartite co-occurrence networks^6,22. These representations are weighted projections of the bipartite network onto each set of physical nodes. C Higher-order multilayer representation of temporal data. In this network, distinct state nodes represent a physical node in each layer where the physical node occurs²⁸. The trajectory of a random walker, guided by the links between the nodes, models network flows³⁸. Network flows are of first order when random walker movements are constrained to single layers and of higher-order when they can move within and between layers²⁸. The aggregation process that simplifies a multilayer network into a single-layer representation alters the network flows, obscuring the modular structures.