The spatial scaling of food web structure across European biogeographical regions

Abstract

The species-area relationship (SAR) is one of the most well-established scaling patterns in ecology. Its implications for understanding how communities change across spatial gradients are numerous, including the effects of habitat loss on biodiversity. However, ecological communities are not mere collections of species. They are the result of interactions between these species forming complex networks that tie them together. Should we aim to grasp the spatial scaling of biodiversity as a whole, it is fundamental to understand the changes in the structure of interaction networks with area. In spite of a few empirical and theoretical studies that address this challenge, we still do not know much about how network structure changes with area, or what are the main environmental drivers of these changes. Here, using the meta-network of potential interactions between all terrestrial vertebrates in Europe (1140 species and 67 201 feeding interactions), we analysed network-area relationships (NARs) that summarize how network properties scale with area. We do this across ten biogeographical regions, which differ in environmental characteristics. We found that the spatial scaling of network complexity strongly varied across biogeographical regions. However, once the variation in SARs was accounted for, differences in the shape of NARs vanished. On the other hand, the proportion of species across trophic levels remained remarkably constant across biogeographical regions and spatial scales, despite the great variation in species richness. Spatial variation in mean annual temperature and habitat clustering were the main environmental determinants of the shape of both SARs and NARs across Europe. Our results suggest new avenues in the exploration of the effects of environmental factors on the spatial scaling of biodiversity. We argue that NARs can provide new insights to analyse and understand ecological communities.

Spatial scaling of soil microbial co‐occurrence networks in a fragmented landscape

“…Recent theoretical and empirical work has revealed potential mechanisms driving changes in food web structure across spatial scales 4–6 . Among those, SARs have been identified as an important driver of NARs 5,6 . In accordance with these studies, we found that SARs were the main factor that drives NARs of soil bacteria and fungi (Figures 2, S1, S3, and S4).…”

Using ecological networks to answer questions in global biogeography and ecology

“…We suggest using high‐resolution assessments over large spatial scales to improve our understanding of ecosystem structure and function. By comparing the properties of ecological networks at different spatial resolutions (50, 10 and 1 km 2 ), it is possible enhance fundamental knowledge (Galiana et al, 2021), but also determine the necessary scales for robust decision‐making based on ecological network data.…”

Graph embedding and transfer learning can help predict species interaction networks despite data limitations

“…"; the most promising solutions involve examining the spatial consistency of network area relationships (Fortin et al, 2021; see e.g. Galiana et al, 2018Galiana et al, , 2019Galiana et al, , 2021, which is impossible in the absence of enough information about the network itself. This suggests that inferred metawebs should be further downscaled to allow for a posteriori analyses.…”