Exposing the structure of an Arctic food web

Abstract

How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator–prey interactions to considering the full set of interacting species.

The use of DNA barcodes in food web construction—terrestrial and aquatic ecologists unite!

“…3), as well as the prey choice of spiders (Wirta et al 2015a) and birds (Wirta et al 2015b), we have resolved a food web much more complex than previously thought (Fig. 3).…”

“…2B; see references in Food web structure is affected by resolution). Interaction strength is often unquantified (from Summerhayes andElton 1923 through Cohen et al 1990 to Wirta et al 2015b), inferred from sometimes limited and always laborious observations of direct attacks (Carnicer et al 2009) or through methods with an only indirect link to realized predation and consumption rates (Frost 1972;Nyffeler 1999;Diehl et al 2013;Majaneva et al 2014). …”

“…For macroscopic animals, we have used CO1 barcodes (Hebert et al 2003); for plants we have used rbcLa and ITS2 (Chen et al 2010;Hollingsworth 2011;Hollingsworth et al 2011;Kuzmina et al 2012). Drawing on the molecular identification tools thus generated, we have verified the identity of each node in the food web (Wirta et al 2016), and reconstructed the trophic links among three key taxa in the local ecosystem: birds, spiders, and insects (Wirta et al 2014(Wirta et al , 2015a(Wirta et al , 2015b.…”

Tundra arthropods provide key insights into ecological responses to environmental change

“…For reasons mentioned above, it is logical to develop and make the first tests of such tools in tundra ecosystems. For instance, molecular tools for species identification offer new opportunities for studying food web dynamics and temporal variation in species interactions (Wirta et al 2015). The lower diversity makes it simpler to develop complete DNA reference libraries in tundra ecosystems (Wirta et al 2016).…”

Life Cycle Impact Assessment in the Arctic: Challenges and Research Needs

“…Seasonality in food web structures introduce challenges in modeling uptake in marine food webs [46], even if Arctic marine and terrestrial food webs are generally short [44]. Terrestrial food web structures in the Arctic are not found different from those at lower latitude [47].…”