The contribution of a drainage network to the spatial and temporal patterns of macroinvertebrate diversity across an agricultural headwater catchment

The headwaters of lowland agricultural catchments in Europe often consist of extensive networks of small field drainage ditches. In comparison to larger freshwater systems, these small habitats are likely to be highly impacted by man, both physically and chemically. Little research has been conducted on drainage ditch ecosystems despite their high percentage contribution to the total length of running water habitat in a catchment and their potential contribution to total catchment freshwater biodiversity. Here, we report on an investigation into the macroinvertebrate species richness patterns of drainage ditches in an intensive agricultural landscape in south-west Ireland. Despite high anthropogenic disturbance in the form of nutrient and fine sediment inputs this study revealed dynamic and diverse community assemblages. Our results highlight the large beta diversity associated with these small waterbodies. The ditch habitats were found to support high numbers of unique and rare taxa, including nationally rare and threatened species.