Hydrology and management of turloughs (temporary lakes) affect marsh fly (sciomyzidae: diptera) communities

Abstract

Hydrology and management affect dipteran communities in wetlands and they, themselves, have the potential to influence prey communities. Turloughs are temporary lakes unique to Ireland. Their vegetation is ecotonal on a dry-wet continuum and, due to differing summer management practises, shows a diversity of vegetation lengths. Marsh flies (Sciomyzidae), a taxon that has potential as wetland bio-indicators, were chosen to investigate management, hydrological and prey effects on turloughs. Summer collections of Sciomyzidae were made on 24 homogeneous zones across ten turloughs. At each position that flies were collected, vegetation surveys were conducted to utilise Ellenberg indices as surrogate environmental variables. Winter collections of Molluscs were made on 21 zones. Sciomyzidae showed maximum total abundance and species richness at sites intermediate on the dry-wet gradient, supporting the intermediate disturbance hypothesis. Indicator species analysis gave site-specific preferences: most species favoured the site with the longest vegetation, but the smallest species showed a significant preference for the site with the shortest vegetation. Across the full hydrological gradient, known terrestrial snail-killers were indicators of drier poor-grasslands and known hygrophilous species were indicators of the wettest zones. Generalised linear models for abundance of the dominant species consistently showed negative relationships with total prey abundance. However, sciomyzid communities showed no significant co-structure with prey communities, but did with sampling conditions, and management/hydrological variables. Sciomyzid communities change qualitatively and quantitatively with vegetation structure and hydrology and correlative evidence for predation pressure by the dominant species highlights the potential of Sciomyzidae to control the intermediate host of fascioliasis.