Tabanids in Europe: the result of 8, 000 years of grazing

In Europe, the animal domestication changed the fauna of ungulates and the landscape by modifying Nemoral forests in a mosaic of wooded, cultivated and grazed plots. From then on, grazing activities acted as a driver for the enhancement of biodiversity. Afterwards, extensive practices have been replaced by more intensive, homogeneous, and large-scale production. As a result, the intensification of practices has created new conditions for parasite transmission and growth, and agricultural practices may have exerted selective pressure favorable to opportunist, competitive, and fast-growing species. Tabanids (Diptera: Tabanidae) are cosmopolitan free-living temporary ectoparasites of livestock which have colonized a wide various type of habitats thanks to their diversity and their adaptibility. Unlike other biting flies such as Stomoxys or Haematobia, they are quite independent of domestic livestock because of their larval habitats and their opportunistic blood-feeding pattern. However, some tabanid species may have been favoured by grazing activities. Therefore, we have characterized the European geographic distribution of tabanids based on published and unpublished datasets from Spain to Bulgaria. The diversity of tabanids is firstly influenced by biogeographical context, but also by grazing activity. Linear mixed-effect models show that tabanid evenness is negatively related to pasture area, and that the relative abundance of Tabanus bromius, the most common species, is positively related to grazing intensity. Thus, grazing activity, occuring in Europe since many centuries, seems to have led to the dominance of T. bromius over all other tabanid species.