Long-Term Changes in Composition and Distribution of Bumblebees in Urban Areas

The distribution of bumblebee species in Wrocław (SW Poland) was studied based on data from ten UTM grid squares between 1879 and 2018, and the composition and abundance of bumblebee species between 2011 and 2018. The results were compared with historical data available for the last 139 years, including published materials and collections of the Museum of Natural History (University of Wrocław). Twenty-six bumblebee species, including six species of cuckoo bumblebees of the subgenus Psithyrus, were recorded. One species was not confirmed during the later period, nine were strongly decreasing both in the range of distribution, seven other were expanding significantly in Wrocław and three were new in the Wrocław city boundaries. Negative and positive tendencies resulted from both anthropogenic and natural factors. All bumblebees that appeared in the city of Wrocław and increased their abundance were species that prefered forest and shrub areas, while species that disappeared from the city and decreased in numbers were species who prefered open areas.