ColonyPersPOLs · Colony Personality and Pace-of-life Syndrome in Bumblebees

Colony Personality and Pace-of-life Syndrome in Bumblebees

In order to achieve the project's objectives, the bumblebee colonies’ personality and colonies' behavioural type were quantified. We performed a deep analysis of the proximate mechanisms underlying colony personality and organizational immunity. We carried out several experiments that allowed us to delineate behavioural traits (activity levels; recovery of foraging behaviour after a predation attempt and tendency to explore alternative foraging options) and their relationship (i.e. whether they form different behavioural types in the studied population). Each behavioural trait was tested several times for each colony, with a few days in between experiments to evaluate its consistency over time. Each single bee activity and the overall colony activity were measured by estimating the individually marked bees’ foraging activity in artificial arenas. To assess the colony boldness-shyness level, we video-recorded bee flights in the "artificial meadow" in response to predation attacks simulated by artificial crab spiders on plastic flowers. To assess each single bee and colony exploration-avoidance level, each colony was initially trained to forage in an artificial meadow containing an array of plastic flowers (type 1). A few hours later a second type of plastic flower (type 2) that varied from the others in colour was presented nearby to the type 1 flowers and the time to approach the new flower was measured for each bee. Correlational tests and multivarite analyses allowed to delineate colonies' behavioural type and behavioural syndromes across colonies. Our results suggest that, across individuals and colonies, there is a correlation between the readiness to switch to novel foraging options and the latency of resuming foraging after predation. This correlation is not easily explicable in terms of differences in sensory or cognitive ability but might be in line with a link between psychological traits such as ‘boldness’ and ‘neophilia’. The data were presented at the ASAB Easter Meeting (2014, Sheffield). Data evaluation is still in progress and a manuscript will be in preparation in the brief time for a main publication. (Baracchi D & Chittka L. Interindividual and intercolony differences in bumblebee responses to novel stimuli and predation threat. In preparation). As part of the project, we quantified the organizational immunity in bumblebee colonies using network and spatial analyses. All bees from several young colonies (n = 20) were individually marked and video-recorded within the nest for a total of 10 hours in three different days. A single bee for each colony was artificially infected. As soon as transmission stages are produced, other bees can pick up the infection and we screened the faeces under the microscope of each bee belonging to all colonies every 7 days for two weeks. Videos were used to determine the interaction network and the position of each bee on the nest before and after infection. Foraging activity outside of the nest was also recorded each time. The contact network and the spatial organization of each single bee within the nest (data evaluation is still in progress) will help in understanding: 1) the differences in the organization immunity among colonies; 2) the consistency of the position of each bee in the social network over time; 3) the observed spread of pathogens within colonies in different colonies. The results of these experiments will show how pathological induced changes in individual bee affect colony organizational immunity, pinpointing causes and consequences of this social organization. Data evaluation is still in progress and a manuscript will be in preparation in the brief time for a substantial publication. (Baracchi D, Brown MJF, Chittka L. Interaction network and pathogen flow within bumblebee colonies). In addition we extended the interest in studying the effect of natural nectar occurring alkaloids in bumblebee behaviour as well as in reducing the pathogen load in bumblebees infected by Crithidia bombi. I carried out this study in collaboration with Prof. Mark Brown (RHUL) and Prof. Lars Chittka (QMUL). In fact, as stated in the project, the ecological and economical importance of bee species, their recent and increasing global change-induced decline has made the study of these species an urgent issue. Given the importance of disease in driving declines of managed honeybees and wild bumblebees, understanding the potential relevance of self-medication to pollinators may be key to understanding and managing these declines. A thorough understanding of the interactions between plants and bee colony productivity and colony health will bring important insights to develop cutting edge strategies for the management of a major pollinator in agricultural systems worldwide. The study resulted in an original publication (Baracchi, Brown and Chittka, 2015, F1000Research) and this research opened an important line of research that is expected to have implications for both policy-making and industry apart from making significant scientific advances.

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