Controlling the impact of the managed honeybee on wild bees in protected areas

Abstract

In recent years, conservation biologists have raised awareness about the risk of ecological interference between massively introduced managed honeybees and the native wild bee fauna in protected natural areas. In this study, we surveyed wild bees and quantified their nectar and pollen foraging success in a rosemary Mediterranean scrubland in southern France, under different conditions of apiary size and proximity. We found that high-density beekeeping triggers foraging competition which depresses not only the occurrence (−55%) and nectar foraging success (−50%) of local wild bees but also nectar (−44%) and pollen (−36%) harvesting by the honeybees themselves. Overall, those competition effects spanned distances of 600–1.100 m around apiaries, i.e. covering 1.1–3.8km2 areas. Regardless the considered competition criterion, setting distance thresholds among apiaries appeared more tractable than setting colony density thresholds for beekeeping regulation. Moreover, the intraspecific competition among the honeybees has practical implications for beekeepers. It shows that the local carrying capacity has been exceeded and raises concerns for honey yields and colony sustainability. It also offers an effective ecological criterion for pragmatic decision-making whenever conservation practitioners envision progressively reducing beekeeping in protected areas. Although specific to the studied area, the recommendations provided here may help raise consciousness about the threat high-density beekeeping may pose to local nature conservation initiatives, especially in areas with sensitive or endangered plant or bee species such as small oceanic islands with high levels of endemism.

Spatial variability in a plant–pollinator community across a continuous habitat: high heterogeneity in the face of apparent uniformity

“…As a managed species introduced in large numbers, honey bee abundance is frequently higher than the abundance of all other pollinator species together (Geslin et al 2017). In our study, honey bees accounted for nearly 72% of the flower visits recorded, one of the highest proportions registered in natural habitats (range: 0–85%, Hung et al ). Consequently, we expected that honey bees would have important effects on the spatial distribution of wild pollinator communities.…”

“…Because as much as 99.1% of honey bee visits were on R. officinalis and T. vulgaris , it is unlikely that honey bees could have any competitive effects on pollinators visiting other, less abundant, flower species. This result may be related to the time of the year (early spring) in which surveys were conducted, corresponding to the peak of flower production in the park (Flo et al ). At that time, flower visitation rates are low compared to late spring, when floral resources sharply decline and a greater number of pollinator species are active (Bosch et al 2009, Filella et al 2013).…”

“…We surveyed 2–4 plots per day between 2 and 17 April . This period corresponds to the flowering peak of the scrubland community (Flo et al ). The field team was composed of eight people trained to identify the pollinator fauna of the study area.…”

“…To describe variation in flower and pollinator community composition across sites we calculated beta‐diversity between plots with the Bray–Curtis quantitative dissimilarity index (Anderson et al 2011) using the ‘betapart’ package (Baselga et al ) for R. As pollinator composition could also be affected by temperature, we performed Mantel tests between pollinator composition (including and excluding honey bees) and differences in maximum temperature between plots. None of these tests were significant (all p > 0.1).…”

“…As a result, temperature was not accounted for in pollinator composition autocorrelation analyses. To check for spatial autocorrelation of flower and pollinator community composition, we performed Mantel correlograms with 9999 permutations using the beta‐diversity indices and the geographical distance between plots implemented in the ‘vegan’ package (Oksanen et al ) for R. In these analyses, sample size was 780 possible combinations of pairs of plots.…”