Nest mounds of red wood ants (Formicaaquilonia): hot spots for litter-dwelling earthworms |
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Authors: | Jouni Laakso Heikki Setälä |
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Institution: | Department of Biological and Environmental Science, University of Jyv?skyl?, P.O. Box 35, FIN-40351 Jyv?skyl?, Finland Fax: +358 14 602321; e-mail: Jouni Laakso: jotla@jyu.fi, FI
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Abstract: | A previously undocumented association between earthworms and red wood ants (Formicaaquilonia Yarr.) was found during an investigation of the influence of wood ants on the distribution and abundance of soil animals
in boreal forest soil. Ant nest mounds and the surrounding soil of the ant territories were sampled. The ant nest mound surface
(the uppermost 5-cm layer) harboured a much more abundant earthworm community than the surrounding soil; the biomass of the
earthworms was about 7 times higher in the nests than in the soil. Dendrodrilusrubidus dominated the earthworm community in the nests, while in soils Dendrobaenaoctaedra was more abundant. Favorable temperature, moisture and pH (Ca content), together with abundant food supply (microbes and
decomposing litter) are likely to make a nest mound a preferred habitat for earthworms, provided that they are not preyed
upon by the ants. We also conducted laboratory experiments to study antipredation mechanisms of earthworms against ants. The
experiments showed that earthworms do not escape predation by avoiding contact with ants in their nests. The earthworm mucus
repelled the ants, suggesting a chemical defence against predation. Earthworms probably prevent the nest mounds from becoming
overgrown by moulds and fungi, indicating possible mutualistic relationships between the earthworms and the ants.
Received: 21 November 1996 / Accepted: 3 April 1997 |
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Keywords: | Dendrobaenaoctaedra Dendrodrilusrubidus Formicarufa nest mound Predator avoidance Mutualism |
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