Diversity and Structure of Hoverfly (Diptera: Syrphidae) Communities in Agricultural Areas in Vojvodina Province (Serbia) A Case Study on Brassica napus L

To gain some insight into the structure of the hoverfly community in fields of oilseed rape (Brassica napus L.), we conducted field experiments over three years (2011-2013) at two localities in the province of Vojvodina, northern Serbia. We recorded a total of 20 hoverfly species. Three species-Episyrphus balteatus (De Geer, 1776), Eristalis tenax (Linnaeus, 1758) and Eupeodes corollae (Fabricius, 1794)-were the most abundant in both localities and in each year. In order to determine the effect of climatic and non-climatic parameters on abundance and diversity of hoverflies, two separate PCA analyses were carried out. Multiple linear regressions were used to examine the relationships between abundance and extracted PC axes, while ordinal multinomial regressions were conducted to determine the relationships between species diversity and extracted PC axes. We did not detect statistically significant correlations between climatic and non-climatic parameters and overall hoverfly abundance. PC axes exhibited slight correlation with species diversity. The first PC axis clearly showed that overall species diversity increases with increasing temperature, relative humidity and diversity of crops surrounding the surveyed plots, whereas PC2 related species composition with monthly average rainfall and the season and year of observation. Synecological analysis of our data indicated that only a few species are major contributors to hoverfly communities on the oilseed rape crops we investigated. However, the importance of less abundant hoverfly species should not be underestimated, as sometimes these species play an important role in pollination in a specific part of the day or season, and this should be considered when creating agricultural policies and regulations, especially when it is known that abundances of hoverflies and pollinators in general are positively correlated with floral abundance and abundance flowering plant species.