Cavity occupancy by wild honey bees: need for evidence of ecological impacts
The European honey bee (Apis mellifera) is managed worldwide for honey production and crop pollination, and is an invasive species in many countries. Wild colonies occupy natural and human‐made cavities and are thought to impact other cavity‐using species. We reviewed documented evidence of wild A mellifera nesting sites globally via a literature review (27 relevant studies) and citizen‐science observations of wild honey bee colonies on iNaturalist (326 observations). Honey bee occupancy rates from published studies were typically low and occupation was often temporary. Citizen‐science data showed that most colonies in cavities had small or narrow entrance holes. Current evidence of perceived competition with honey bees in cavities is largely anecdotal and little is known about the long‐term impacts on survival and reproductive success of other cavity‐occupying species. To guide conservation policy and practice, more empirical research is needed to understand the ecological outcomes of competitive interactions in nesting cavities.
The missing links: Bee and non-bee alpine visitor observation networks differ to pollen transport networks
1. A majority of the world’s flowering plants benefit from insect pollination. Bees in particular are known to carry large amounts of pollen, and the pollen load transported is often highly conspecific. However, there is limited knowledge about the transfer of pollen by other non-bee flower-visiting insect taxa.
2. We observed and collected insects visiting flowers in an Australian alpine plant community. We identified insect body pollen loads to evaluate the relative differences among taxa using visitation and pollen transport networks. We sampled a diverse pollinator community from 39 insect families that visited 31 plant species (n = 488 individual insects).
3. Pollen abundance and richness on insect bodies varied significantly among Diptera, Hymenoptera and Lepidoptera both among individuals and across insect families.
4. Bees carried more pollen overall than the other three insect orders surveyed, yet dipterans were the most frequent flower visitors overall, with six dipteran families observed visiting flowers more frequently than the most frequent hymenopteran visitor (Apis mellifera L.). Apidae was also the only family in this study to carry consistently large quantities of pollen.
5. At the order level, Diptera carried the second highest quantity of pollen but greater diversity of pollen than other insect orders. Importantly, visitation networks revealed visits to plant taxa that were not identified in pollen transport networks and vice versa.
6. Given the missing links in both visitor observation and pollen transfer networks, we advocate combining both types of networks to provide a more accurate estimate of the full range of plant–pollinator interactions occurring within and across taxa at the community level. Understanding the variation in plant–pollinator interactions as a result of differences among taxa and between networks of flower visitors, pollen transfer is important to evaluate the level of generalisation/specialisation among plants and their pollinator partners.
Industry needs matter—Incorporating stakeholder interests in the selection of flower resources to support pollinators
1. Most pollinator policy initiatives are focused on habitat restoration and increas-ing the availability of floral resources, yet the choice of plant species is not always compatible with farming system cultivation and management needs.
2. In this paper, we developed a framework for selecting plants to specifically meet stakeholder needs. We trialled 19 plant species and collected observational data on plant-insect visitors, plant survival in the orchard environment and potential risks to crops and the environment. We used this framework to identify plants suitable to incorporate into blueberry cropping systems.
3. Practical implication: Our framework ensured plant choice based on informed decisions and allowed the selection of two plant species that aligned well with industry needs. Different plants may be optimal for different conservation aims, hence plants selected need ideally to be evaluated for their use by the flower-visiting taxa, as well as align with industry growing practices and needs.
Weather Conditions Affect the Visitation Frequency, Richness and Detectability of Insect Flower Visitors in the Australian Alpine Zone
Weather conditions, such as humidity, temperature, and wind speed, affect insect activity. Understanding how different taxa respond to varying environmental conditions is necessary to determine the extent to which environmental change may impact plant-pollinator networks. This is particularly important in alpine regions where taxa may be more susceptible to extreme climatic events and overall increases in temperature. We observed plant-flower visitor interactions in Australian alpine plant communities to determine 1) the structure of the plant-flower visitor community, and 2) how floral visitation and diversity of insect taxa varied according to environmental conditions and habitat type. Coleoptera and Diptera were the most dominant flower visitors in the visitation networks. Most insect orders were moderately generalized in their interactions, but Hymenoptera showed greater specialization (d') at exposed sites compared to other insect orders. Importantly, insect orders behaved differently in response to changes in environmental conditions. Hymenoptera visitation increased with higher temperatures. Diptera was the only taxon observed actively moving between flowers under inclement conditions. Our results demonstrate the value in sampling across the spectrum of environmental conditions to capture the differences among flower visiting insect taxa in their responses to varying environmental conditions. A diversity of responses among insect taxa could facilitate community-level resilience to changing environmental conditions.