To date, research on changes in the bee fauna focused mainly on agricultural areas. Bee fauna in urbanized areas, on the other hand, has not been thoroughly explored. Our previous studies, as well as those by other authors, show that cities are important habitats for a considerable number of bee species. Since urbanization is an ever on-going process it is important to investigate the influence of urban areas on these insects.
Previous studies show that in city centres small-sized bee species are more numerous than in areas beyond cities. Body size of bees is one of the key determinants of reproductive success of both bees and plant species that the insects visit. Thus, the aim of the research was to verify whether urbanization causes changes in the body size of individuals within one species. Moreover, the research allowed for determining the occurrence of developmental disorders manifested as body asymmetry in bees.
Study plots were ordered by the gradient of urbanization from areas of densely developed area of the high urbanization level in the strict city centre, through spaciousless densely build-up areas of house estates with blocks of flats, areas of detached houses, big urban green areas within city borders to areas located beyond the city.
Ten out of 11 traits significantly deviated from symmetry, indicating directional asymmetry (DA). Directional asymmetry (DA) is another form of bilateral asymmetry which differs from FA in that one side is consistently larger than the other. Fluctuating asymmetry (FA) is widely used as a measure of developmental stability. At the same time some researchers suggest that DA itself may also be a potential indicator of developmental stability. Our results show that DA differed between habitats. Bees in suburban and urban habitats were less asymmetric as compared to farmland. Furthermore body length of bees did not show differences among the studied habitats. Our results indicate that urban habitats can provide appropriate developmental conditions for bees.