Inferring predator–prey interactions in food webs

Abstract

1. Food webs are a powerful way to represent the diversity, structure, and function of ecological systems. However, the accurate description of food webs requires significant effort in time and resources, limiting their widespread use in ecological studies. Newly published methods allow for the inference of feeding interactions using proxy variables. Here, we compare the accuracy of two recently described methods, as well as describe a composite model of the two, for the inference of feeding interactions using a large, well-described dataset.2. Both niche and neutral processes are involved in determining whether or not two species will form a feeding link in communities. Three different models for determining niche constraints of feeding interactions are compared, and all three models are extended by incorporating neutral processes, based on relative abundances.The three models compared here infer niche processes through (a) phylogenetic relationships, (b) local species trait distributions (e.g., body size), and (c) a composite of phylogeny and local traits.3. We show that all three methods perform well at predicting individual species interactions, and that these individual predictions scale up to the network level, resulting in food web structure of inferred networks being similar to their empirical counterparts. 4.Our results indicate that inferring food web structure using phylogenies can be an efficient way of getting summary webs with minimal data, and offers a conservative test of changes in food web structure, particularly when there is low species turnover between sites. Inferences made using traits require more data, but allows for greater understanding of the mechanisms underlying trophic interactions. A composite model of the two methods provides a framework for investigating the importance of how phylogeny, trait distributions, and relative abundances, affect species interactions, and network structure. K E Y W O R D S body size, food web inference, food web structure, neutral theory, niche model, traitmatching, WebBuilder | 357 Methods in Ecology and Evoluঞon POMERANZ Et Al.

Finding missing links in interaction networks

“…In most cases, ecologists constructing a network have access to (sometimes considerable) additional information and expertise on the study system. Introducing pre-existing knowledge about likely or forbidden interactions, or pooled knowledge from multiple sample sites offers considerable opportunities to maximise the information in a network (Gray et al 2015, Pomeranz et al 2018). External information would be particularly useful in separating ‘forbidden links’ (Olesen et al 2011) that never occur due to fundamental incompatibilities from those that occur elsewhere but not within those spatio-temporal boundaries.…”

Plant-pollinator interaction linkage rules are altered by agricultural intensification

“…Thompson et al, 2012; Tylianakis, Laliberté, Nielsen, & Bascompte, 2010; Vázquez & Aizen, 2004). In a world of increasing human development and rapid environmental change, understanding the drivers behind the formation of pairwise species interactions is a nontrivial but critical challenge for ecologists (Bartomeus et al, 2016; Berlow et al, 2009; Gray et al, 2014; Harvey, Gounand, Ward, & Altermatt, 2017; Hutchinson et al, 2019; Olito & Fox, 2015; Pomeranz, Thompson, Poisot, & Harding, 2019; R. Thompson et al, 2012).…”

“…However, collecting interaction data is costly and time-consuming. Therefore, accurate predictive models of species interactions would be a boon to interaction network research (Bartomeus et al, 2016; Gonzales et al, 2018; Gray et al, 2014; Jordano, 2016; Kaiser-Bunbury & Blüthgen, 2015; Monteiro & Faria, 2018; Pomeranz et al, 2019). Despite the potential applications, a robust and predictive understanding of the rules that determine the formation of species interactions remains elusive.…”

“…For example, whether a pollinator’s tongue can reach the nectar at the base of a flower corolla or if the gape size of a predator is large enough to eat a prey species. Indeed, some studies have found that for a suite of interaction types only a few traits are needed to accurately predict a significant number of the interactions in an interaction network (Bartomeus, 2013; Bartomeus et al, 2016; Berlow et al, 2009; Eklöf et al, 2013; Monteiro & Faria, 2018; Pomeranz et al, 2019; Santamaría & Rodríguez-Gironés, 2007). On the other hand, species abundance may also determine the linkage rules of interactions (i.e.…”

“…On the other hand, species abundance may also determine the linkage rules of interactions (i.e. neutral processes; Canard et al, 2012; Poisot et al, 2015; Vázquez & Aizen, 2004), as the relative abundance of species has been found to accurately predict interaction network structure (Bartomeus et al, 2016; Olito & Fox, 2015; Pomeranz et al, 2019; Vázquez, Chacoff, & Cagnolo, 2009).…”