Space heterogeneity, space use and short-range dispersal in Diptera: A case study

This study investigates the impact of landscape heterogeneity on community structure and population dynamics in two families of Diptera (Empididae and Chironomidae). Adult emergence is compared with aerial flow by means of emergence traps and yellow traps on a transect across four habitats (pond banks, woodland, grassland and heathland) in close proximity to each other. Empids use different space units according to their larval development, sexual behaviour and food requirements. This creates an intermingling of species and individuals originating from different habitats in the lowest part of the transect. Adult chironomids of aquatic species exhibit a preferential use of open habitats while adults with terrestrial larvae disperse largely above the four sites. Habitat fragmentation and heterogeneity lead to opposite patterns in chironomid distribution: some species disperse over the whole set of macrohabitats but others are confined to a single patch, resulting in population isolation. The impact of spatial and temporal landscape patterning is discussed with a view to community structure, life-history tactics and population dynamics.