Spatial analyses of multi‐trophic terrestrial vertebrate assemblages in Europe

Abstract

Aim Although much has been said on the spatial distribution of taxonomic and phylogenetic diversity of vertebrates, how this diversity interacts in food webs and how these interactions change across space are largely unknown. Here, we analysed the spatial distribution of tetrapod food webs and asked whether the variation in local food web structure is driven by random processes or by natural and anthropogenic factors. Location Europe. Time period Present. Major taxa studied Tetrapods. Methods We combined an expert‐based food web (1,140 species and 70,601 links) of all European tetrapods with their respective spatial distributions. We mapped 17 different food web metrics representing complexity, chain length, vertical diversity and diet strategy across Europe and tested whether their distribution reflects the spatial structure of species richness using a null model of food web structure. To avoid multicollinearity issues, we defined composite descriptors of food web structure that we related to a set of environmental layers summarizing both natural and anthropogenic influences and tested their relative importance in explaining the spatial distribution of European terrestrial vertebrate food webs. Results Of the 17 metrics, 10 showed a non‐random spatial distribution across Europe and could be summarized along two major axes of variation in food web structure. The first was related to species richness, mean trophic level and the proportion of intermediate species, whereas the second was related to the connectance and proximity of species within the web. Both descriptors varied with latitudinal gradient. The best descriptors of food web structure were mean annual temperature and seasonality (negatively correlated with the first axis), and human footprint (positively correlated with the second axis). Main conclusions We demonstrate the importance of climate and anthropogenic pressure in shaping the spatial structure of European tetrapod food webs.

TETRA‐EU 1.0: A species‐level trophic metaweb of European tetrapods

“…For each species, we gathered information on species‐specific trophic links plus a set of 11 trophic items: mushrooms, mosses/lichens, algae, detritus, seeds–nuts–grains, fruits, other plant parts, invertebrates, fish, domestic animals and faeces. These diet items could then be used as basal food items in the network (see Braga et al, 2019; O’Connor et al, 2020).…”

“…This could yield false negatives in our dataset (i.e., interactions that exist in nature but that we characterized as non-existent because the literature fails to document those interactions). Using the approach proposed by Morales-Castilla et al (2015), it is possible to use data on species' ecology (e.g., habitat preferences) and distribution (for example considering the data presented in Maiorano et al 2013) to distinguish potential trophic links (what we reported) from trophic links actually occurring (see Braga et al 2019 andO'Connor et al 2020).…”

“…Wherever possible, we considered literature sources focusing specifically on trophic interactions of species measured or inferred in our study area. This dataset has recently been used to investigate the environmental drivers of local network structure in Europe (e.g., connectance; Braga et al, 2019) and the functional structure of the different trophic groups and their spatial structure (O’Connor et al, 2020). In the Supporting Information, we have added an example of the type of analysis that could be carried out with our dataset and the associated R script (Supporting Information Appendices S1–S3).…”

A Roadmap Toward Predicting Species Interaction Networks (Across Space and Time)

“…Because we almost can, and because we definitely should. A better understanding of species interactions, and the networks they form, would help unify the fields of community, network, and spatial ecology; improve the quantification of the functional relationships between species (Dehling and Stouffer 2018;O'Connor et al 2020); re-evaluate metacommunities in light of network structure (Guzman et al 2019); and enable a new line of research into the biogeography of species interactions (Massol et al 2017;Braga et al 2019) which incorporates a synthesis of both Eltonian and Grinnellian niche (Gravel et al 2019). Further, the ability to reliably predict and forecast species interactions would inform conservation efforts for protecting species, communities, and ecosystems.…”

Switching from mesopredator to apex predator: how do responses vary in amphibians adapted to cave living?

“…Thus, understanding their behavioural modulation can greatly help unravel predator-prey interaction mechanisms. Even though being a meso-or an apex predator is generally related to body size, with larger predators preying upon smaller ones (Eklov and Svanback 2006;Donadio and Buskirk 2016), the position of a species within food webs is strongly context dependent and may differ between habitats and ontogenic stage (Ritchie and Johnson 2009;Braga et al 2019). In streams without fish, dragonfly larvae are a classical example; at early life-stages, these organisms occupy an intermediate position in the food webs while, once they grow, they become the apex predators (Hopkins et al 2011;Start 2018).…”