Causes and consequences of inter-individual variability in social insects

• Applicant: Dr. Anja Weidenmüller
• Subject Area: Sensory and Behavioural Biology
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259098174

Animals in social groups often show consistent differences in their behavioural responses. How does this variability arise; and what effects does it have on collective properties of the group? I will address these fascinating questions in detail, using social insects as model system. I will use thermoregulation in colonies of bumblebees as experimental systems that I have well established over the past years. In this project, I have four main objectives that are tightly interconnected and reach from the proximate mechanisms underlying the behavioural differences among the workers of a colony to the ultimate consequences of such inter-individual variability. Each experiment takes a novel perspective on questions relevant for our understanding of collective behaviour and self-organization. (1) One potentially important and little explored mechanism underlying interindividual variability in social insects is preimaginal experience. Environmental fluctuations in e.g. temperature during larval development may be a source of phenotypic variation. In a first step, I will establish the range of temperatures that bumblebee brood is naturally exposed to. Using these temperatures, I will then raise brood (pupae) under different stable or fluctuating temperatures and later observe the behaviour of the adult bees both within their colonies and in an experimental chamber on a brood dummy. Finally, I will expose brood of sexuals (queens and drones) to different temperatures, let them establish colonies, and analyze the thermoregulative behaviour of their brood for possible epigenetic effects.(2) A second important mechanism underlying the behavioural differentiation of workers is experience. I will address the role of experience, specifically of task efficiency and experience on individual task specialization of thermoregulating bumblebees. It is commonly assumed that division of labour leads to highly efficient specialists, however, few empirical studies have documented the effect of experience on efficiency, or of efficiency on experience, and even less studies exist on tasks besides foraging, where the efficiency of a behaviour is not directly correlated to some kind of direct reward. (3) Ultimately, interindividual variability is considered a key feature for division of labour, colony flexibility and colony fitness. However, a direct test of the effect of interindividual behavioural variability on a fitness relevant collective trait is still lacking. I will experimentally manipulate and directly measure the impact of interindividual variability in temperature response behaviour within a group of bumblebee workers on their collective ability to homeostatically regulate brood temperature.(4) Finally, all results obtained in theses experiments will be used to improve existing self-organization models and to test new hypotheses about the importance of interindividual variability on self-organized collective responses of an insect colony.

• DFG Programme: Research Grants