Introduction: Special issue on species interactions, ecological networks and community dynamics – Untangling the entangled bank using molecular techniques

In the last paragraph of the Origin of Species, Darwin (1859) marvels at the diversity of life forms, the complexity of links between them, and the forces creating this “tangled bank”. In this text, we may see the origins of community ecology – today defined as ‘the study of the interactions that determine the distribution and abundance of organisms’ (Krebs, 2009). To capture and quantify the key elements of this concept of community structure, we may conveniently describe communities as ecological networks (Hagen et al. 2012). In such networks, the nodes are formed by species (or other taxonomic units) and the links by their interactions (Gravel et al., 2018).