Aboveground impacts of a belowground invader: how invasive earthworms alter aboveground arthropod communities in a northern North American forest |
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Authors: | Malte Jochum Lise Thouvenot Olga Ferlian Romy Zeiss Bernhard Klarner Ulrich Pruschitzki Edward A. Johnson Nico Eisenhauer |
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Affiliation: | 1. German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Puschstrasse 4, 04103 Leipzig, Germany ; 2. Leipzig University, Institute of Biology, Puschstrasse 4, 04103 Leipzig, Germany ; 3. J.F. Blumenbach Institute of Zoology and Anthropology, University of Goettingen, Untere Karspuele 2, Goettingen 37073, Germany ; 4. Department Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4 |
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Abstract: | Declining arthropod communities have recently gained a lot of attention, with climate and land-use change among the most frequently discussed drivers. Here, we focus on a seemingly underrepresented driver of arthropod community decline: biological invasions. For approximately 12 000 years, earthworms have been absent from wide parts of northern North America, but they have been re-introduced with dramatic consequences. Most studies investigating earthworm-invasion impacts focus on the belowground world, resulting in limited knowledge on aboveground-community changes. We present observational data on earthworm, plant and aboveground arthropod communities in 60 plots, distributed across areas with increasing invasion status (low, medium and high) in a Canadian forest. We analysed how earthworm-invasion status and biomass impact aboveground arthropod community abundance, biomass and species richness, and how earthworm impacts cascade across trophic levels. We sampled approximately 13 000 arthropods, dominated by Hemiptera, Diptera, Araneae, Thysanoptera and Hymenoptera. Total arthropod abundance, biomass and species richness declined significantly from areas of low to those with high invasion status, with reductions of 61, 27 and 18%, respectively. Structural equation models suggest that earthworms directly and indirectly impact arthropods across trophic levels. We show that earthworm invasion can alter aboveground multi-trophic arthropod communities and suggest that belowground invasions might be underappreciated drivers of aboveground arthropod decline. |
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Keywords: | belowground aboveground earthworm invasion insect decline forest Canada |
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