Short-range spatial patterning of terrestrial Chironomidae (Insecta: Diptera) and farmland heterogeneity

Most work considering the effects of landscape structure and heterogeneity on biodiversity in farmland has been devoted to mammals or birds. Despite their worldwide distribution in many different soil types, the ecology of terrestrial Chironomidae is still poorly known. The influence of landscape heterogeneity on the short-range spatial distribution of adult terrestrial Chironomidae within three agricultural landscapes was investigated in Brittany (France). One hundred and twenty-eight yellow pan traps collecting flying individuals emerging from surrounding habitats were set in pairs on the soil surface of crop fields at the bottom of bordering hedges throughout the three sites. Chironomids abundance data were related to nine environmental factors using co-inertia analyses. The terrestrial chironomid community, which included 11 species, was dominated numerically by a semi-terrestrial species, Limnophyes minimus (Mg.), and a true terrestrial species, Smittia pratorum (G.). Amongst environmental factors, disturbance level, land cover, soil hydromorphy, and vegetation height had a significant influence on the distribution of species at all sites. Hedge quality and soil flooding were also significant factors at two of the three sites. Specific life-history traits (including larval and adult ecological requirements) interact with landscape heterogeneity to determine the short-range spatial patterning of species. This work, which provides the first detailed study of adult terrestrial chironomids in farmland, shows that management of crop fields and hedges by farmers has a strong influence on landscape heterogeneity and, consequently, on the spatial distribution of species.