Efficient visual learning by bumble bees in virtual-reality conditions:Size does not matter

Recent developments allowed establishing virtual-reality (VR) setups to study multiple aspects of visual learning in honey bees under controlled experimental conditions. Here, we adopted a VR environment to investigate the visual learning in the buff-tailed bumble bee Bombus terrestris. Based on responses to appetitive and aversive reinforcements used for conditioning, we show that bumble bees had the proper appetitive motivation to engage in the VR experiments and that they learned efficiently elemental color discriminations. In doing so, they reduced the latency to make a choice, increased the proportion of direct paths toward the virtual stimuli and walked faster toward them. Performance in a short-term retention test showed that bumble bees chose and fixated longer on the correct stimulus in the absence of reinforcement. Body size and weight, although variable across individuals, did not affect cognitive performances and had a mild impact on motor performances. Overall, we show that bumble bees are suitable experimental subjects for experiments on visual learning under VR conditions, which opens important perspectives for invasive studies on the neural and molecular bases of such learning given the robustness of these insects and the accessibility of their brain.

Phenotypic plasticity of floral traits and pollination adaption in an alpine plant Pedicularis siphonantha D. Don when transplanted from higher to lower elevation in Eastern Himalaya

Phenotypic plasticity and/or pollinatormediated selection may be responsible for the changes in floral traits of plants when they are forced to live in new conditions. Although the two events could be independent, we hypothesized that phenotypic plasticity in floral traits might help to coordinate plant-pollinator interactions and enhance plant reproductive success in changing habitats. To test this hypothesis, we investigated floral traits and pollination on three natural populations of a lousewort(Pedicularis siphonantha) ranging at different elevations, as well as two downward transplanted populations in Shangeri-La County and Deqin County, northwest Yunnan, China. The results indicated that floral traits, i.e. phenology, longevity,display size, corolla tube length and pollen production differed significantly among populations. Moreover,or the two transplanted populations, floral traits diverged from their original populations, but converged to their host populations. Although the phenotypic plasticity in floral traits might be a rapid response to abiotic factor such as warmer environment, the changes in floral traits were found to be well adapted to pollination environment of the host population. Compared with plants of their original habitats in higher elevation, the transplanted individuals advanced flowering time, shortened flower longevity, reduced floral display size and pollen production, received higher visiting frequency and yielded more seeds. These findings suggested that phenotypic plasticity of floral traits might help plants adjust their resource allocation strategy between preand post-pollination stages in response to harsh or temperate conditions, which might correspondingly meet a pollinator-poor or hyphen rich environment.This would be beneficial for the widely-distributed species to adapt to various environmental changes.

Floral trait variation across individual plants within a population enhances defense capability to nectar robbing

Floral trait variation may help pollinators and nectar robbers identify their target plants and,thus,lead to differential selection pressure for defense capability against floral antagonists.However,the effect of floral trait variation among individuals within a population on multi-dimensional plant-animal interactions has been little explored.We investigated floral trait variation,pollination,and nectar robbing among individual plants in a population of the bumble bee-pollinated plant,Caryopteris divaricata,from which flowers are also robbed by bumble bees with varying intensity across individuals.We measured the variation in corolla tube length,nectar volume and sugar concentration among individual plants,and evaluated whether the variation were recognized by pollinators and robbers.We investigated the in-fluence of nectar robbing on legitimate visitation and seed production per fruit.We found that the primary nectar robber(Bombus nobilis)preferred to forage on plants with long-tubed flowers,which produced less nectar and had lower sugar concentration compared to those with shorter corolla tubes.Individuals with shorter corolla tubes had comparatively lower nectar robbing intensity but higher visitation by legitimate visitors(mainly B.picipes)and higher seed production.Nectar robbing signifi-cantly reduced seed production because it decreased pollinator visits.However,neither pollination nor seed production differed between plants with long and short corolla tubes when nectar robbers were excluded.This finding suggests that floral trait variation might not be driven by pollinators.Such variation among individual plants thus allows legitimate visitors and nectar robbers to segregate niches and enhances population defense against nectar robbing in unpredictable conditions.

Survey of insect visitation of ornamental flowers in Southover Grange garden, Lewes, UK

Ornamental flowers commonly grown in ttrban gardens and parks can be of value to flower-visiting insects. However, there is huge variation in the number of insects attracted among plant varieties. In this study, we quantified the insect attractiveness of 79 varieties in full bloom being grown in a public urban garden that is popular due to its beautiful flowers and other attractions. The results showed very clearly that most varieties （77%, n = 61） were either poorly attractive or completely unattractive to insect flower visitors. Several varieties （19%, n = 15） were moderately attractive, but very few （4%, n = 3） were highly attractive. Closer examination of Dahlia varieties showed that ＂open＂ flowered forms were approximately 20 times more attractive than ＂closed＂ flowered forms. These results strongly suggest that there is a great potential for making urban parks and gardens considerably more bee- and insect-friendly by selecting appropriate varieties.