SPATIAL-DISTRIBUTION OF SPIDERS ON THE FLOODPLAIN OF THE RIVER TRENT,UK - THE ROLE OF HYDROLOGICAL SETTING

Invertebrate communities provide sensitive indicators of physical stre ss, such as that imposed by moisture regime. With reference to two flo odplain sectors-one non-regulated and one regulated-on the River Trent , UK, this paper uses spider communities to characterize the dominant floodplain units (riparian, wetland, wet woodland, pasture and arable) and compares the information derived with a parallel data set from th e groundbeetle community (F. Carabidae). The study yielded 77 spider s pecies, of which 43 were common to the two floodplain sectors. Hypomma bituberculatum (wetland), Bathyphantes niginus (wet woodland) and Pac hygnatha degeeri, Pardosa pullata and Trochosa ruricola (arable) showe d restricted distributions and are regarded as 'habitat specialists'. Species richness was highest in the wetland patches and lowest in the pasture. Differences between the faunal communities of the different h abitats were greatest in the regulated sector. Spiders and beetles col lected from the same traps are shown to provide different and compleme ntary information on floodplain functioning, which may prove valuable in any ecological assessment.