Aleksandra Langowska

Mass-flowering invasive plants can generate strong floral resource pulses, but their effects on pollinator communities are unlikely to be uniform across taxa. We investigated how flowering stands of invasive Canadian goldenrod ( Solidago canadensis ) shape pollinator assemblages at an intermediate stage of invasion in a Central European suburban landscape, by comparing paired goldenrod-dominated and non- Solidago plots with diverse co-flowering vegetation located within the same suburban landscapes where S. canadensis was already present. During two flowering seasons, we sampled wild bees, butterflies, hoverflies, and honey bees, and tested how plot type, urbanization intensity (impervious surface area, ISA), and site-level goldenrod cover were associated with pollinator abundance, richness, diversity, and community composition. Pollinator community composition differed significantly between goldenrod-dominated and control plots. Goldenrod-dominated plots supported higher honey bee and hoverfly abundance, but lower wild bee abundance and lower butterfly abundance and species richness. By contrast, wild bee richness and alpha diversity, as well as hoverfly richness, did not differ significantly between plot types, indicating assemblage reorganization rather than consistent taxon loss. Associations between honey bee abundance and wild bee metrics also reversed between plot types, suggesting that flowering S. canadensis can alter local patterns of pollinator co-occurrence around concentrated floral resources. Overall, our results show that, during the flowering peak, a mass-flowering invader can restructure pollinator use of floral patches by disproportionately attracting managed and generalist visitors, while other guilds are less strongly represented in goldenrod-dominated vegetation. These findings indicate that, at an intermediate stage of invasion, the ecological effects of mass-flowering invasive plants may involve taxon-specific redistribution of pollinator activity among floral patches rather than uniform changes in pollinator diversity.

Quercetin is a biologically active flavonoid compound that exerts numerous beneficial effects in humans and animals, including anti-diabetic activity. Its action has been explored in rodent models of type 1 and type 2 diabetes. It was revealed that quercetin mitigated diabetes-related hormonal and metabolic disorders and reduced oxidative and inflammatory stress. Its anti-diabetic effects were associated with advantageous changes in the relevant enzymes and signaling molecules. Quercetin positively affected, among others, superoxide dismutase, catalase, glutathione peroxidase, glucose transporter-2, glucokinase, glucose-6-phosphatase, glycogen phosphorylase, glycogen synthase, glycogen synthase kinase-3β, phosphoenolpyruvate carboxykinase, silent information regulator-1, sterol regulatory element-binding protein-1, insulin receptor substrate 1, phosphoinositide 3-kinase, and protein kinase B. The available data support the conclusion that the action of quercetin was pleiotropic since it alleviates a wide range of diabetes-related disorders. Moreover, no side effects were observed during treatment with quercetin in rodents. Given that human diabetes affects a large part of the population worldwide, the results of animal studies encourage clinical trials to evaluate the potential of quercetin as an adjunct to pharmacological therapies.

Varroa destructor is the main pest of the honey bee Apis mellifera, causing colony losses. We investigated the effect of temperature on the autumn abundance of V. destructor in bee colonies over 1991–2020 in Central Europe. We tested the hypothesis that temperature can affect autumn mite populations with different time-lags modulating the bee abundance and brood availability. We showed that raised spring (March–May) and autumn (October) temperatures reinforce autumn V. destructor infestation in the bee colonies. The critical temperature signals embrace periods of bee activity, i.e., just after the first cleansing flights and just before the last observed bee flights, but no direct effects of phenological changes on V. destructor abundance were found. These effects were potentially associated with increased bee reproduction in the specific periods of the year and not with the extended period of activity or accelerated spring onset. We found significant effects of autumn bee abundance, autumn capped brood abundance, and the number of colonies merged on autumn mite infestation. We also observed differences in V. destructor abundance between bees derived from different subspecies. We indicated that climatic effects, through influence on the bee abundance and brood availability, are one of the main drivers regulating V. destructor abundance.

The honey bee, Apis mellifera, has been extensively used as a model in gerontological research, although the presence of adult males has been a factor so far neglected in investigations of the social regulation of worker aging. In the honey bee, drones (males) are produced and maintained only in the swarming season, or if a colony loses its queen. Here, we report on the longevity cost incurred by queenless workers that provide care for adult drones under conditions of food resources limited to hydrocarbons only. We found that the presence of drones reduced the life expectancy of workers, even if the workers were prevented from direct contact with the drones (double-mesh-type test). At the same time, the survival rate of the drones was surprisingly high. This suggests that our results reveal the existence of a mechanism that drones use to increase their fitness. We hypothesize that drones are able to communicate their presence to workers without direct contact. Alternatively, queenless workers might try to recruit other individuals to take care of males. In both cases, queenless workers, which are not able to reproduce themselves when deprived of protein, dramatically respond to the presence of drones.

Bee-eaters (Meropidae) are considered agricultural pests and their presence provokes conflicts with beekeepers and farmers who rely on the pollination services of honey bees. This problem is often deal with through the mass killing of the birds, even though the quantitative evidence on the impact of bee-eaters on honey bee colonies is scarce. The current paper reports the performance of honey bee colonies protected with mist nets from migrating flocks of European bee-eaters Merops apiaster in Israel. In the study the weight gains of bee hives surrounded by mist nets were 6.44 times higher than that of unprotected hives (26.4 kg vs. 4.1 kg). The results confirmed that bee-eaters locally pose a problem to apiaries and potentially to the crops that require pollination. Mist- netting appeared to be an effective mitigation method for alleviating conflicts between beekeepers and bee-eaters. However, the study also showed that bees were able to differentiate between their main predator and other avian species trapped in mist nets and stung only bee-eaters. Moreover, the bees were targeting the most vulnerable body parts of birds which resulted in some bird fatalities. Therefore, due to accidental mortal- ity of birds, mist-netting is recommended only on the migratory routes in cases when bee hives cannot be moved to other areas.