Effects of spatial scale of sampling on food web structure

Abstract

This study asks whether the spatial scale of sampling alters structural properties of food webs and whether any differences are attributable to changes in species richness and connectance with scale. Understanding how different aspects of sampling effort affect ecological network structure is important for both fundamental ecological knowledge and the application of network analysis in conservation and management. Using a highly resolved food web for the marine intertidal ecosystem of the Sanak Archipelago in the Eastern Aleutian Islands, Alaska, we assess how commonly studied properties of network structure differ for 281 versions of the food web sampled at five levels of spatial scale representing six orders of magnitude in area spread across the archipelago. Species (S) and link (L) richness both increased by approximately one order of magnitude across the five spatial scales. Links per species (L/S) more than doubled, while connectance (C) decreased by approximately two-thirds. Fourteen commonly studied properties of network structure varied systematically with spatial scale of sampling, some increasing and others decreasing. While ecological network properties varied systematically with sampling extent, analyses using the niche model and a power-law scaling relationship indicate that for many properties, this apparent sensitivity is attributable to the increasing S and decreasing C of webs with increasing spatial scale. As long as effects of S and C are accounted for, areal sampling bias does not have a special impact on our understanding of many aspects of network structure. However, attention does need be paid to some properties such as the fraction of species in loops, which increases more than expected with greater spatial scales of sampling.

The geographical variation of network structure is scale dependent: understanding the biotic specialization of host–parasitoid networks

“…Similarly, our results show the importance of considering different spatial scales to get a broader understanding of the specialization pattern and their determinants. Additionally, if network structure varies across spatial scales (Pillai et al 2011, Roslin et al 2014, Wood et al 2015, Galiana et al 2018), then network studies estimating the causes of variation in network structure along any environmental gradient (Dormann et al 2017, Tylianakis and Morris 2017, Pellissier et al 2018) might benefit from understanding the spatial scaling of network structure along the gradient. However, caution must be exerted when interpreting the comparison between different spatial scales.…”

“…Some of the specialization metrics considered can be sensitive to differences in species richness (S) among networks (Bengtsson 1994, Baiser et al 2012, Poisot and Gravel 2014, Wood et al 2015). Therefore, comparative analyses of networks need to control for variation in species richness across webs given that conclusions on the variability of network specialization might simply result from variation in species richness across webs.…”

Bringing Elton and Grinnell together: a quantitative framework to represent the biogeography of ecological interaction networks

“…First, most documented metawebs have thus far considered ecological interactions to be deterministic, rather than probabilistic (Havens 1992, Wood et al 2015. First, most documented metawebs have thus far considered ecological interactions to be deterministic, rather than probabilistic (Havens 1992, Wood et al 2015.…”

Spatial analyses of multi‐trophic terrestrial vertebrate assemblages in Europe

“…Food web ecology has focused on the trophic relationships between species within discrete communities, with the goal of inferring the underlying processes acting upon them, such as the relationship between species diversity and food web structure, community assembly processes and even robustness of those communities to species extinctions (Montoya, Pimm, & Solé, ). However, since the pioneering work of Kitching () on latitudinal gradients of aquatic food web structure, food web ecology has shifted from finding food web structural generalities across distinct communities to searching for large‐scale spatial distribution of ecological networks, such as latitudinal gradients, and relationships with climate and resource availability (Kortsch, Primicerio, Fossheim, Dolgov, & Aschan, ; Montoya & Galiana, ; Pellissier et al, ; Poisot, Guéveneux‐Julien, Fortin, Gravel, & Legendre, ; Post, ; Roslin et al, ; Wood, Russell, Hanson, Williams, & Dunne, ).…”