PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 36 - Pollination ecology I
L-13, Lobby Level, Cook Convention Center
Presiders: S Travers and R Spigler
Episyrphus balteatus: an example of pollination efficiency in hover flies.
Jauker, Frank*,1, Wolters, Volkmar1, 1 Justus Liebig University, Giessen, Giessen, Germany
ABSTRACT- There is increasing concern about the worldwide decline of pollinating insects and their associated ecological services. Despite the unquestionable importance of honey bees and wild bees, the resulting economical and ecological threats can only be fully assessed when other pollinating taxa differing in ecological strategies are also considered. As a contribution to this aim a study on the pollination efficiency of the common hover fly Episyrphus balteatus is presented. While adult hover flies visit flowers and are thus often referred to as pollinators, their influence on seed set of plants has rarely, if ever, been examined. The two-year study was carried out in isolation cages (8 m3) on summer rape (Brassica napus). In the first year, two densities of hover flies and a control were tested in four cages each, in the second year, four cages with individuals of the red mason bee Osmia rufa were added for a comparative approach. The results clearly demonstrate a significant positive effect of pollinating insects on the seed set of rape. Effects differed among taxa, however, with bees having a greater impact on the number of seeds per pod, but only hover flies increasing thousand seed weight. This is the first experimental evidence for hover flies being important pollinators in cultural landscapes. Our results suggest complementing ecological roles of hover flies and bees due to strong differences in factors such as habitat preference. Furthermore, hover flies as efficient pollinators might also play a crucial role in the conservation of wild flower populations.
Key words: pollination, Episyrphus balteatus, arable land