Tundra ecosystems are often unproductive, and peaks in resource availability are highly variable in space and time. Therefore, the success of organisms inhabiting these biomes likely depends on their ability to efficiently exploit heterogeneously distributed resources. We assessed how orb-weaving spider (Larinioides patagiatus) aggregations near Lake Mývatn, Iceland, respond to large midge (Diptera: Chironomidae) emergences that subsidize ecological communities in the surrounding landscape. The emergences occur for only a few weeks each summer, and the subsidy declines with distance from the lakeshore, producing large spatiotemporal variation in prey availability that might drive orb-weaver foraging behavior. We conducted three surveys during different phases of the summer emergence along a distance gradient to quantify variation in spider aggregation, web size, and habitat use in response to prey abundance. We found that aggregation size increased with the abundance of aerial prey, with the highest orb-weaver densities occurring at peak midge emergence. In contrast, changes in web size did not vary with midge abundance, but rather were determined by physical habitat structure. Our results illustrate how orb-weaver aggregations and web building can respond to spatiotemporal variation in resource subsidies across ecosystem boundaries.
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We would like to thank B. Blundell, C. Daws, S. Grover, and C. Miller for assistance with data collection, Jamie Botsch for assistance creating maps, and Árni Einarsson for comments on the manuscript and logistical research support. We would also like to thank two anonymous reviewers, whose feedback greatly improved the manuscript. This work was supported by NSF LTREB DEB-1556208 to ARI and NSF Graduate Research Fellowship to JSP (DGE-1256259).
Bultman H, Hoekman D, Dreyer J, Gratton C (2014) Terrestrial deposition of aquatic insects increases plant quality for insect herbivores and herbivore density: terrestrial effects of midge deposition. Ecol Entomol 39:419–426. doi:10.1111/een.12118CrossRefGoogle Scholar
Carpenter SR, Cole JJ, Pace ML et al (2005) Ecosystem subsidies: terrestrial support of aquatic food webs from 13C addition to contrasting lakes. Ecology 86:2737–2750. doi:10.1890/04-1282CrossRefGoogle Scholar
Halaj J, Ross DW, Moldenke AR (1998) Habitat structure and prey availability as predictors of the abundance and community organization of spiders in western Oregon forest canopies. J Arachnol 26:203–220Google Scholar
Herberstein ME, Tso I-Min (2000) Evaluation of formulae to estimate the capture area and mesh height of orb webs (Araneoidea, Araneae). J Arachnol 28:180–184CrossRefGoogle Scholar
Hoechstetter S, Walz U, Dang L, Thinh N (2008) Effects of topography and surface roughness in analyses of landscape structure—a proposal to modify the existing set of landscape metrics. Landsc Online 3:1–14. doi:10.3097/LO.200803CrossRefGoogle Scholar
McCormick MI (1994) Comparison of field methods for measuring surface topography and their associations with a tropical reef fish assemblage. Mar Ecol Prog Ser Oldendorf 112:87–96CrossRefGoogle Scholar
Nentwig W, Blick T, Gloor D, Hänggi A, Kropf C (2017) Larinioides patagiatus (Clerck, 1757). Spiders of Europe. https://araneae.unibe.ch/data/964. Accessed 31 July 2017
Orr M, Zimmer M, Jelinski DE, Mews M (2005) Wrack deposition on different beach types: spatial and temporal variation in the pattern of subsidy. Ecology 86:1496–1507. doi:10.1890/04-1486CrossRefGoogle Scholar
Polis GA, Hurd SD (1995) Extraordinarily high spider densities on islands: flow of energy from the marine to terrestrial food webs and the absence of predation. Proc Natl Acad Sci 92:4382–4386CrossRefPubMedGoogle Scholar
Polis GA, Anderson WB, Holt RD (1997) Toward an integration of landscape and food web ecology: the dynamics of spatially subsidized food webs. Annu Rev Ecol Syst 28:289–316CrossRefGoogle Scholar
QGIS Development Team (2014) QGIS geographic information system. Open Source Geospatial Foundation. http://qgis.osgeo.org
R Core Team (2014) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/
Riechert SE, Tracy CR (1975) Thermal balance and prey availability: bases for a model relating web-site characteristics to spider reproductive success. Ecology 56:265–284CrossRefGoogle Scholar