The use of Syrphidae as functional bioindicator to compare vineyards with different managements

Hoverflies (Diptera Syrphidae) were studied in two vineyards in Northern Italy, to characterize the fauna of a conventional farm in comparison with one with organic management. Hoverfly populations were monitored in three different years (2010, 2011 and 2012) using Malaise traps as the sampling technique. In three years, a total of 48 species were recorded in the two vineyards. Among those, seven species found across three years were not expected in accordance with predictions from the nature of the surrounding habitats (via Syrph the Net). Some of these species are usually associated with dry grassland and may be considered as associated with vineyards, increasing the fauna of these productive habitats. The total number of species seem to be highly similar in the two vineyards, despite the different management. The use of functional traits was much more useful in understanding the differences between the two vineyards. Despite the small distance between the two sites, hoverfly populations were different in the three years. The presence of different habitats adjacent to the two vineyards seem to be the main feature affecting hoverfly populations. In addition, the organic vineyard showed a higher percentage of species associated with the herb and root layers. These taxa can be associated with the adjacent wood and/or with the vineyard since the latter is characterized by an improved vegetation management typical of an organic system (e.g. the grass cover technique). The analysis of functional traits in the Syrphidae allowed an ecological interpretation confirmed by the habitat analysis and farm inputs. Functional analysis based on the hoverfly fauna proved to be a synthetic and informative tool to characterize and interpret a number of complex features in a standard and simple way.