A categorization of recent network approaches to analyse trophic interactions

Abstract

Summary1. Network analysis, a branch of discrete mathematics that quantifies the structure of links between a set of nodes, is emerging as a powerful methodology to approach complex ecological interactions. 2. There has been a rapidly increasing body of research targeting the topological description of trophic interactions. Here we categorize studies applying a topological approach to empirical trophic networks, with the aim of identifying recent trends and deficiencies in this approach to analyse trophic interactions.3. There were biases in the taxonomic groups addressed and in the methodological approaches used for data collection and analyses. Studies on antagonistic interactions were generally focused on a single kind of bipartite interaction, and most studies compared network attributes across time, ecosystems or treatments. 4. We encourage a broader use of both interlinked and unipartite networks that would allow for describing indirect effects of trophic interactions, as well as time series of networks across seasons and phenological states of organisms. We also noted shortages of studies identifying interaction structures across levels of organization, on the correspondence between network structure and function, and particularly of studies on the behaviour of trophic networks in the face of environmental perturbations, which could provide guidance for preserving ecological interactions.

Network topology of stable isotope interactions in a sub-arctic raptor guild

“…To describe the structure of isotope relationships between the different study species and age classes, we adapted network tools derived from graph theory (Miranda et al 2013). We conducted our analyses on separate age classes partly since certain prey may have been favoured to bring back to the nests (e.g., Lindström 1994;Catry et al 2016), and partly because the isotopes in adult and juvenile feather reflected different time periods.…”

“…However, despite its applicability to predation processes, topological approaches to study trophic interactions within predator assemblages have been surprisingly neglected (Miranda et al 2013). In an ecological context, a trophic network typically consists of two sets of discrete nodes that are connected through links representing resource use (Elton 1927), where the nodes usually represent species or other recognizable taxonomic units, although exceptions exists (e.g., Miranda et al 2014).…”

“…It may therefore be fruitful to also re-project bipartite networks into unipartite ones (Newman 2001;Opsahl 2009), which then will link species on the same trophic level through interactions quantified from shared resources (Padrón et al 2011). Unipartite projections of trophic interactions can hold useful information regarding intraguild processes, such as competition and facilitation among species (Miranda et al 2013), as well as ecosystem properties of consumer guilds (Dunne et al 2002;Jordán 2009). They may also aid in identifying ecologically important species (Jordán et al 2006) and to identify species most likely to be influenced by ecosystem perturbations such as biological invasions (Carvalheiro et al 2008).…”

Interaction patterns within a multi-herbivore assemblage derived from stable isotopes

“…Here we expand on these applications to also enable interpretations of ecological interaction structures from stable isotope data (see also Yeakel et al, 2013). Such an approach is highly timely, since it builds on a rapid development both on theoretical and methodological expansion of topological approaches to ecological studies (Miranda et al, 2013), and it expands the scope of ecological information that can be derived from stable isotope studies. Since characterisations of isotope niches encapsulate information both on the taxonomic identity of the resources as well as on the physiology of these resources and the area within which they were assimilated, consumer-isotope network may hold information on a wider range of ecological processes than trophic networks derived directly from consumer and resource taxonomic groups.…”

“…In parallel with the re-emerging interest in community ecology, network analyses have been increasingly used to describe and quantify species trophic relationships (Ings et al, 2009;Miranda et al, 2013). A trophic network consists of at least two distinct sets of nodes (typically species) that are connected through resource utilization links (Elton, 1927;Harary, 1961).…”