Floodplain connectivity, disturbance and change: a palaeoentomological investigation of floodplain ecology from south-west England.

1. Floodplain environments are increasingly subject to enhancement and restoration, with the purpose of increasing their biodiversity and returning them to a more 'natural' state. Defining such a state based solely upon neoecological data is problematic and has led several authors to suggest the use of a palaeoecological approach. 2. Fossil Coleopteran assemblages recovered from multiple palaeochannel fills in south-west England were used to investigate past floodplain and channel characteristics during the mid- to late-Holocene. Ordination of coleopteran data was performed using Detrended Correspondence Analysis (DCA) and produced clear and discrete clustering. This clustering pattern is related to the nature of the environment in which assemblages were deposited and hence channel configuration and dynamics. 3. The DCA clustering pattern is strongly related to measures of ecological evenness, and a strong relationship between these indices and the composition of the water beetle assemblage within samples was revealed. Repeating the ordination with presence-absence data results in a similar pattern of clustering, implying that assemblage composition is crucial in determining cluster placement. 4. As assemblage composition is primarily a function of floodplain topography and hence disturbance regime, we attempt to relate these data to the Intermediate Disturbance Hypothesis (IDH). A significant positive correlation was found between ecological diversity (Shannon's H') and Axis 1 of all ordinations in predominantly aquatic assemblages.