Meeting Abstract
The Eurasian yellow star-thistle (Centaurea solstitialis L., Asteraceae) is a highly invasive weed that has become established in western United States. In natural and agricultural environments of its invasive range, C. solstitialis produces high amounts of nectar per floret and is predominantly visited by honeybees. The opposite case appears to occur in its native range. In semi-natural areas of Lesvos, Greece, C. solstitialis produces low volumes of nectar and are visited by a diverse group of bees, but rarely or never visited by honeybees. Herein we document the visitation pattern of bees on C. solstitialis in an urban environment of its native range. We also explore the relationship of bee body size and nectar availability. Studies were conducted during July 2015 in patches of C. solstitialis established in abandoned lots at the Uludağ University campus in Bursa, Turkey. A total of 41 species, including honeybees, belonging to five families and 19 genera were recorded. Not a single bee species dominated the visits, although small species of the families Megachilidae and Halictidae bees were common. Average nectar standing crop volume per floret was low (0.003 to 0.117 μl) and average bee head was not significantly correlated with nectar availability in the studied patches. Analyses of pollen loads as well as direct observations of bee foraging behavior suggest that a large number of bees visit C. solstitialis for nectar only. These results are similar to previous observations on native populations of C. solstitialis in natural or semi-natural landscapes. They also support the observed differences in the pollinator interactions of C. solstitialis across continents.
