Raghavendra Gadagkar

Centre for Ecological Sciences
Research Areas: 
Animal behaviour, ecology, evolution, social life of insects
Research Highlights: 

Prof Raghavendra Gadagkar has been working on a primitively eusocial wasp called Ropalidia marginata, for more than 30 years, employing field, laboratory, theoretical and experimental work on the species. Using biochemical and molecular techniques, the group has shown that queens mate multiply and mix sperm from different males. Using pedigrees, they could show that workers rear distantly related brood. Experiments have shown that workers are unlikely to discriminate between different classes of relatives and that all individuals are not equally fit for social or solitary life. Prof Gadagkar also made a ground breaking contribution by developing a new class of theories, the focus of which is demography; his Assured Fitness Returns model is an example of how group living can confer advantages over solitary life that are independent of genetic relatedness. The group also examines proximate questions of social organization and queen-worker interaction. Queens of R.marginata are behaviourally docile, meek sitters. This raises questions regarding how such queens become queens in the first place, how they inhibit worker reproduction and how they regulate non-reproductive activities of their workers. Attempts to answer these questions have begun to suggest that R.marginata queens start their career as aggressive queens and probably switch to pheromonal control of worker reproduction, which is why they can afford to be behaviourally meek sitters. As a response to this behaviour on the part of their queens, the workers have responded by self-organizing their own non-reproductive activities and thereby gaining indirect fitness without much prodding by the queen. Another remarkable feature of Ropalidia marginata society is the smooth and conflict-free succession that happens from one queen to the next. Through a series of experiments, we have demonstrated that even though human observers cannot predict the identity of the successor, the wasps themselves appear to know who the successor would be in the event of the death or loss of the queen. Indeed we have demonstrated that there is a long reproductive queue of cryptic successors with designated positions in the queue and all this happens in the presence of the old queen.

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