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How do bees move across the landscapes? The ERC Consolidator Grant “Pollination ecology: how do bees move across the landscape and fashion plant reproduction (Bee-Move)” aims to link the study of bee spatial foraging patterns in the field with pollen dispersal and plant reproduction success. It will identify key mechanisms of pollination on which we could act for ecological, economic or public health issues.

It is often assumed that social life imposes specific cognitive demands for animals to communicate, cooperate and compete, ultimately requiring larger brains. The “social brain” hypothesis is supported by data in primates and some other vertebrates, but doubts have been raised over its applicability to other taxa, and in particular insects. Here, we review recent advances in insect cognition research and ask whether we can identify cognitive capacities that are specific to social species. One difficulty involved in testing the social brain hypothesis in insects is that many of the model species used in cognition studies are highly social (eusocial), and comparatively little work has been done in insects that live in less integrated social structures or that are solitary. As more species are studied, it is becoming clear that insects share a rich cognitive repertoire and that these abilities are not directly related to their level of social complexity. Moreover, some of the cognitive mechanisms involved in many social interactions may not differ from those involved in non-social behaviors. We discuss the need for a more comparative and neurobiologically grounded research agenda to better understand the evolution of insect brains and cognition.

International audience; Navigation by honey bees refers to the cognitive and behavioral mechanisms bees of the genus Apis use to move between a location and one or multiple goals. These involve the evaluation and integration of direction and distance cues as well as the learning of specific places. For honey bees, goals can be as diverse as the colony nest, a foraging site, a new nesting site, or an open-air mating area.

Understanding how pollinators move across space is key to understanding plant mating patterns. Bees are typically assumed to search for flowers randomly or using simple movement rules, so that the probability of discovering a flower should primarily depend on its distance to the nest. However, experimental work shows this is not always the case. Here, we explored the influence of flower size and density on their probability of being discovered by bees by developing a movement model of central place foraging bees, based on experimental data collected on bumblebees. Our model produces realistic bee trajectories by taking into account the autocorrelation of the bee’s angular speed, the attraction to the nest (homing), and a gaussian noise. Simulations revealed a « masking effect » that reduces the detection of flowers close to another, with potential far reaching consequences on plant-pollinator interactions. At the plant level, flowers distant to the nest were more often discovered by bees in low density environments. At the bee colony level, foragers found more flowers when they were small and at medium densities. Our results indicate that the processes of search and discovery of resources are potentially more complex than usually assumed, and question the importance of resource distribution and abundance on bee foraging success and plant pollination.

Figures S1-S3

1. Accuracy of the environment generator. 2. Expected values of average nutritional states (p/c) for random food intakes in environments with two asymmetrically imbalanced foods (Fig. 1C).

Table S1. Mean number of flowers visited per bee during each bin of eight foraging bouts, their standard deviations, as well as the maximum and minimum number of flowers. Table S2. Frequency of bee-flower associations obtained from network modules calculated using the DIRTLPAwb+ algorithm [31]. Rows refer to bee identity. Columns refer to flower identity. Figure S1. Experimental set-up. The outdoor flight cage (length = 44 m, width = 20 m, height = 3 m, mesh size = 0.5 mm) was erected on a flat pasture at the Centre for Agricultural Bioscience International (CABI) in Egham (Surrey, UK). Artificial flowers (F1-F10) with their webcams were connected to five laptop computers, each protected by a golf umbrella. A sixth laptop was used to power a webcam at the colony nest entrance. Picture by ML. Figure S2. Artificial flowers. An electric syringe pump filled with sucrose solution is connected through a plastic tube to the feeding cup (capacity = 40 μL). Sucrose solution (40% v/v) is pushed into the feeding cup at a constant rate (3.3 μL/min). Bees have access to the sucrose solution through a hole in the middle of the horizontal platform. A webcam (video camera connected to a laptop computer running motion sensitive software) pointing at the flower records each movement occurring on the landing platform. Each time a bee enters the camera’s field of view a video clip is recorded (minimum duration = 5 s) giving information about the identity of the bee (tag number), its arrival and departure time, and any interaction with other foragers on the flower. Picture by ML. Figure S3. Flower visitation matrices and computed modules. Y axis: flower identity. X axis: bee identity. Black-white gradients in each cell represent the frequency of visits made by each bee to each flower (darker colours denote higher visitation frequency). Complete visitation sequences can be found in dataset S1. Red polygons are the modules obtained from the DIRTLPAwb+ algorithm. (DOCX 4514 kb)