Abstract
Large‐scale patterns in species diversity and community composition are associated with environmental gradients, but the implications of these patterns for food‐web structure are still unclear. Here, we investigated how spatial patterns in food‐web structure are associated with environmental gradients in the Barents Sea, a highly productive shelf sea of the Arctic Ocean. We compared food webs from 25 subregions in the Barents Sea and examined spatial correlations among food‐web metrics, and between metrics and spatial variability in seawater temperature, bottom depth and number of days with ice cover. Several food‐web metrics were positively associated with seawater temperature: connectance, level of omnivory, clustering, cannibalism, and high variability in generalism, while other food‐web metrics such as modularity and vulnerability were positively associated with sea ice and negatively with temperature. Food‐web metrics positively associated with habitat heterogeneity were: number of species, link density, omnivory, path length, and trophic level. This finding suggests that habitat heterogeneity promotes food‐web complexity in terms of number of species and link density. Our analyses reveal that spatial variation in food‐web structure along the environmental gradients is partly related to species turnover. However, the higher interaction turnover compared to species turnover along these gradients indicates a consistent modification of food‐web structure, implying that interacting species may co‐vary in space. In conclusion, our study shows how environmental heterogeneity, via environmental filtering, influences not only turnover in species composition, but also the structure of food webs over large spatial scales.
Highlights
It is well established that species’ diversity and composition vary along environmental gradients (Worm and Myers 2003, Tittensor et al 2010, Blois et al 2013), but the implications of these patterns for food-web structure remain unclear (Cirtwill et al 2015, Morris et al 2015)
A main source of variation in food-web structure along environmental gradients is driven by turnover in species composition due to environmental filtering (Pellissier et al 2017), and by trait matching between co-occurring species (Tylianakis and Morris 2017)
We investigate large-scale variation in food web structure along environmental gradients across the Barents Sea
Summary
It is well established that species’ diversity and composition vary along environmental gradients (Worm and Myers 2003, Tittensor et al 2010, Blois et al 2013), but the implications of these patterns for food-web structure remain unclear (Cirtwill et al 2015, Morris et al 2015). Most large-scale spatial studies of ecological interactions are performed on relatively few (i.e. two or three) interacting species, functional. In addition to select for specific traits, environmental conditions may influence food-web structure via effects on whole community diversity and trophic complexity, for example along productivity gradients (Neutel et al 2007), where trophically more complex communities (e.g. species-rich, link-rich, with many trophic levels and long path lengths) develop under adequate supply and availability of resources
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