Photo credit: www.sciencedaily.com
The introduction of managed honey bees to new regions can impact local native bee populations, but a study from Penn State indicates that under specific circumstances, native bees can recover once honey bee colonies are relocated.
The findings, published in the Journal of Insect Science, investigated the implications of migratory beekeeping, a practice where beekeepers transport honey bee colonies to different spots during the year, on indigenous bee communities.
The research revealed a significant decrease in both the numbers and diversity of native bees when honey bees were introduced to an area. However, in sites where apiaries had been established for years and were then removed, there was a resurgence in native bee populations, leading to increased overall numbers and diversity of species.
Margarita López-Uribe, an expert in entomology and co-author of the study, stated that these results imply that, while the movement of managed bees can disrupt native populations, recovery is plausible. She noted, “The rebound of native bees occurred within a year following the removal of apiaries, which indicates that their populations did not entirely vanish but were temporarily displaced.” She emphasized that these bees were able to thrive again due to the availability of diverse flowers and minimal agricultural disturbance, including the limited use of pesticides.
However, López-Uribe cautioned that the situation may vary in regions that lack floral diversity or space and where managed honey bee colonies are more densely packed.
The broader context reveals a troubling trend: insect populations are in decline globally due to various human activities that alter habitats and introduce non-native species. While these introduced species can positively impact certain crops, they may also lead to competition with native species, as observed with honey bees competing with local bee populations for floral resources.
Conducting research on this competition can be challenging due to the ubiquity of honey bees. For their study, the researchers focused on the unique setting of the Qinghai-Tibet Plateau in China, where honey bees do not naturally inhabit and are present only due to migratory beekeeping practices, with each apiary ranging from 60 to 100 colonies.
López-Uribe explained, “Beekeepers have been moving their hives to higher altitudes during the hot summer months for the last forty years, where cooler conditions and abundant floral resources prevail, compounded by minimal pesticide exposure due to the absence of agriculture.”
Initially, the team intended to survey two types of sites: those actively hosting honey bee colonies and others that had never supported them. An unexpected opportunity arose when a music festival was held in a location that previously had migratory apiaries, enabling the researchers to also examine areas where honey bees had been kept for decades but removed the year before.
The researchers selected two plots at each site type to collect samples, gathering bees on three separate occasions for classification as either honey bees or native species.
Analysis of the gathered data indicated that native bee populations were most diminished at sites currently occupied by honey bees, while those populations surged in locations that either had previously hosted honey bees or had never included them. A notable reduction was observed specifically among the dominant native bee species, Andrena sp. 3, a type of mining bee. Although total native bee numbers improved at sites where honey bees were removed, the population of Andrena sp. 3 did not experience a corresponding recovery.
The researchers further noted that the phylogenetic diversity of native bees, which reflects the evolutionary relationships among species within a community, was highest at sites currently occupied by honey bees and even greater at sites that had previously hosted them. This pattern suggests that as A. sp. 3 populations dwindled, other species benefited from increased access to limited foraging and nesting resources.
While the study occurred in China, López-Uribe believes the implications may extend to various regions globally. She noted, “Our study involved up to 100 colonies per migratory apiary, which is relatively small compared to the 1.5 million colonies transported to California annually. Therefore, similar results could emerge in regions with lower colony numbers.”
The overall conclusions indicate that while the influx of managed honey bees tends to lower native bee populations, the enduring impact is likely influenced by the quantity of honey bee colonies introduced and their duration of stay. Future investigations could further explore how varying densities and lengths of presence of honey bee colonies affect native bee abundance, community composition, and pollination functions through different seasons.
Co-authors of the study include Anthony Vaudo from the U.S. Forest Service, Michael Orr from the Staatliches Museum für Naturkunde Stuttgart, Qing-Song Zhou and Chao-Dong Zhu from the Chinese Academy of Sciences, and Junpeng Mu from Mianyang Normal University. Financial support was provided by multiple entities, including the U.S. Department of Agriculture National Institute of Food and Agriculture and the Chinese Academy of Sciences.
Source
www.sciencedaily.com