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Lake-derived midges increase abundance of shoreline terrestrial arthropods via multiple trophic pathways

Authors


J. Dreyer, Dept of Zoology, Univ. of Wisconsin-Madison, 145 Noland Hall, 250 North Mills Street, Madison, WI 53706-1708, USA. E-mail: jmdreyer@wisc.edu

Abstract

Aquatic insects link adjacent ecosystems by transporting nutrients, energy, and material as they move from bodies of water into terrestrial habitats. Insects emerging from streams and rivers are known to benefit arthropod predators such as spiders, but their influence may extend to other arthropod feeding groups as well. We conducted a terrestrial arthropod survey at a series of lakes spanning a strong gradient of midge (Chironomidae, Diptera) emergence. These small, short-lived insects reach high densities in some areas such that their carcasses litter the ground, and serve as a potential resource for non-predatory arthropods. Our study revealed that arthropod assemblages in areas of high midge density were significantly different from those with few midges, the result of an increase of all taxa rather than changes in taxonomic composition. Eight of nine terrestrial arthropod taxa sampled showed a strong positive response to the presence of midges including detritivores and herbivores in addition to predators. Taxa that could consume living or dead midges directly responded especially strongly to midge gradients. Our results strongly suggest that midges enter the terrestrial arthropod food web through multiple pathways, increasing numbers of a wide range of arthropods. Furthermore, they emphasize the importance of lakes as sources of aquatic insects that significantly alter processes in the neighboring terrestrial environment.

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