Riparian ground beetles (Coeloptera, Carabidae) preying on aquatic invertebrates: a feeding strategy in alpine floodplains |
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Authors: | Daniel Hering Harald Plachter |
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Institution: | Fachbereich Biologie, Fachgebiet Naturschutz, Philipps-Universit?t Marburg, D-35032 Marburg, Germany Fax: +49 6421 288985; e-mail: hering@mailer.uni-marburg.de, DE
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Abstract: | The food and feeding habits of riparian ground beetles were studied in four alpine floodplains (Bavaria, Germany): a 5th-order
stream (the Isar) and three 3rd-order streams. The riparian fauna along the streams mainly consists of predaceous species.
Riparian ground beetle densities were much higher along the Isar than along the small streams. Aquatic invertebrates composed
89% of the potential prey for carnivorous terrestrial insects along the Isar. Besides aquatic organisms washed ashore, stoneflies
emerging on land are of considerable importance as potential prey for terrestrial predators. In contrast, only 34% of the
potential prey organisms collected along the small streams were of aquatic origin. Food abundance was 9 times higher in the
shore region of the Isar compared to the small streams. Surface drift in the Isar, a potentially important food source for
riparian organisms, was about 106 organisms and exuviae per meter stream width in 24 h. The drift density in the Isar was 59 times higher than that in a small
stream. Terrestrial organisms provided only 3% of the drifting particles in the Isar, but 50% in the small stream. Gut content
analysis reveals, that riparian ground beetles in the Isar floodplain mainly feed on aquatic organisms washed ashore or emerging
on land. While small Bembidion species prefer chironomids (larvae and adults) the larger species Nebria picicornis feeds on emerging stoneflies, terrestrial riparian organisms and aquatic organisms accumulating along the shoreline. The
prey of riparian ground beetles in the floodplain of the three small streams mainly consists of terrestrial species some of
which may have been washed ashore.
Received: 2 September 1996 / Accepted: 26 February 1997 |
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Keywords: | Aquatic-terrestrial interactions Carabidae Gut content analysis Riparian zone Surface drift |
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