The effects of succession on aggression and foraging dynamics in Polistes dominula
Date: 24 June 2019
University of Exeter
MSc by Research in Biological Sciences
Eusocial insects have been the subject of a great deal of attention from bioscientists since at least as early as the mid-1960s, and the social structure of some were researched even before the term “eusocial” had been introduced. Polistes dominula is an incredibly well researched species, the first invertebrate to have its dominance ...
Eusocial insects have been the subject of a great deal of attention from bioscientists since at least as early as the mid-1960s, and the social structure of some were researched even before the term “eusocial” had been introduced. Polistes dominula is an incredibly well researched species, the first invertebrate to have its dominance hierarchy documented, but there are still unanswered questions regarding how and why their linear hierarchies persist and flourish when unrelated helpers have the option of founding a nest singly. Investigating the dynamics surrounding these altruistic aggregations may contribute a wealth of knowledge to the current understanding behind sociality and dominance as a concept. This thesis investigates some of the important aspects of Polistes dominula hierarchical societies, focusing namely on aggressive interactions and helping effort. The specific aim of this study is to identify the consequences of new leadership on aggression and foraging efficiency, particularly around the point of succession. In Chapter 1 a large sample of relevant studies are critically reviewed to provide a summary of the current understanding of Polistes dominula societies. This chapter highlights the biggest questions not yet conclusively answered about social evolution, and this species as a model of linear dominance hierarchies. This is for the purposes of introducing relevant discoveries, indicating which gaps this research is aiming to fill, and which questions future researchers should be trying to answer. Following this review is an outline of the general methods that apply to this study as a whole, including reasoning behind the study species, study site, and methods of data collection (Chapter 2). In Chapter 3 the results of a dominant removal experiment, aiming to test the role of aggression in hierarchy establishment and maintenance among foundresses, are reported. No evidence was found that suggested that aggression was used by a successor to establish herself as the new dominant. Similarly, there was no evidence found that suggested aggression displayed by a successor was influenced by the aggression displayed by the original dominant. In Chapter 4 another dominant removal experiment tested whether foraging effort of the nest collectively changed during succession. The results of this experiment suggested that foraging effort decreased from the day a foundress was removed, regardless of her rank, to the end of the sample period. This pattern was seen whether the foundress removed was the dominant or a low-ranking individual. Therefore, there was no evidence that foraging effort decreases specifically during periods of succession, but rather when any other foundress disappears. Foraging effort did not differ significantly between control and treatment groups but did significantly decrease from the day of removal once a foundress had been taken from the nest. This is possibly because remaining wasps became more vigilant following the disappearance of a nest-mate, or because the disappearance of any foundress causes instability in the social hierarchy, driving the rest of the nest to commit more time to dominance contests. These findings are put into context and their contributions towards the field are described in Chapter 5. A description of how this research contributes towards the synthesis of a broader understanding of Polistes dominula is provided, along with suggestions for further research that builds on these findings and those before it.
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