Abstract
In their pristine state, river landscapes consist of complex mosaics of aquatic and terrestrial habitats. They are highly dynamic and, with their harsh environments, offer living space for many specialists. In the present study, the habitat choice of specialists of the riparian arthropod community was studied on a near-natural stretch of the Upper Isar River. Study period was between May and July 2011. Araneae, Formicidae and Staphylinidae were the most common taxa. The dominant species was Pardosa wagleri with 1,092 individuals, followed by Arctosa cinerea with 184 and Paederidus rubrothoracicus with 154 individuals. These three species made up 54% of all located individuals and were considered as representatives for the invertebrate community. Remaining species had by far smaller proportions and were not determined further due to the low individual numbers. Habitat preferences for the three dominant species were analyzed using negative binomial regression. Common and important habitat features were non-silted and coarse gravel areas, which are neighboured by patches with an elevation 1m above the water. Furthermore, the absence of vegetation cover as well the absence of ants was crucial for the occurrence of the three model species. Habitat preferences were subject to seasonal influences due to various requirements of different life stages. Other influencing factors were competition and predation due to Formicidae and larger individuals of Lycosidae. This demonstrates the high importance of structurally rich riverbeds with a mosaic of distinct habitat patches for the three representative species. Our findings are a valuable contribution for the conservation and management of braided rivers and their characteristic gravel bar biocoenosis.