University of Bayreuth, Press Release Nr. 039/2023, 03.04.2023
Ecological-Botanical Garden of the University of Bayreuth is a hotspot for wild bees in Central Europe
214 wild bee species, and thus a little more than 40 per cent of the bee species found in Bavaria, were detected last year in the Ecological-Botanical Garden of the University of Bayreuth (ÖBG) as part of a master's thesis. Among them were four species threatened with extinction, such as Ammobates punctatus, as well as numerous other endangered species.
Bees are the most important pollinators worldwide and are not only indispensable for the preservation of wild plant species, but also for the pollination of a large part of our crops. Bees are thus considered an ecologically and economically very important group with indispensable ecosystem functions. Worldwide, however, fewer and fewer bee species have been recorded since the 1990s. Against this background, the high number of species of 214 wild bee species found in the Ecological Botanical Garden (ÖBG) is very pleasing.
In his Master's thesis, Daniel Schanz mapped the wild bees of a 13.5 hectare section of the ÖBG's open space in almost 40 inspections from March to September 2022. This was the second study of the wild bee fauna in the ÖBG after its first survey in 2000. In addition, he recorded the flower-visiting behaviour of native and non-native plant species. The work was supervised by Prof. Dr. Elisabeth Obermaier (ÖBG, University of Bayreuth) and Prof. Dr. Stefan Dötterl (University of Salzburg), who carried out the survey in 2000. Compared to the survey 22 years ago, the 85 newly added bee species are often more heat-loving and significantly less widespread northwards than bee species with a record in both surveys.
14 of the species detected in 2000 could not be detected in 2022, so that in the last 20 years a total of almost 230 bee species have been detected in the ÖBG, which is 44 percent of the species known in Bavaria and 39 percent of the species known in Germany. This makes the ÖBG one of the most species-rich wild bee sites in Central Europe, even in relation to its relatively small area. Even in no other botanical garden in Central Europe have so many bee species been recorded so far.
"The high number of species in the ÖBG is mainly justified by the high habitat diversity in a small area and with many different flowering plants and nesting areas," says Daniel Schanz. "These include the willow culture with flower-rich ground vegetation, many rarely mown meadow areas, the useful plant garden and the Calluna heath, as well as a sandy slope for ground-nesting species. In addition, dead wood provides further opportunities for species that rely on such structures to establish their nesting sites." In the ÖBG, spontaneously emerging wild herbs are also tolerated in many places, and their importance for the bee fauna can be considered very high.
The survey of plant species visited by bees in 2022 showed that among the 16 plant species visited by the greatest diversity of bee species, only two were non-native flowering plants. About half of these 16 plant species were not directly planted wild herbs. Particularly large numbers of bee species were found on dandelion, mountain bluebell, yarrow, man's litter, meadow bluebell, horned clover, round-leaved bellflower and wild carrot. Among them were mostly so-called oligolectic species, which are specialised on certain plants with regard to flower pollen.
Overall, the studies prove that the ÖBG with its many native plant species and diverse nesting opportunities is a hotspot for bees in Central Europe.
"Against the background of an increasing intensification of the cultivated landscape with fewer and fewer habitats for wild bees, near-natural gardens are becoming more and more important, also for endangered bee species," emphasises Prof. Dr. Elisabeth Obermaier. "Furthermore, the study shows that the bee fauna has changed significantly within 22 years." Among the newly added species, quite a few are particularly heat-loving, such as the Halictus subauratus, which has already become more common than the Halictus tumulorum. Prof. Dr. Stefan Dötterl therefore states: "The bee fauna in the ÖBG is clearly responding to climate warming".