Sociality and Ageing: Longevity and Reproductivity in a Social Insect

Fischer, Liliana Rebekka (2025) Sociality and Ageing: Longevity and Reproductivity in a Social Insect. Doctoral thesis, University of East Anglia.

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Abstract

Sociality and ageing represent major evolutionary features but how they interact remains relatively little understood. Eusocial insects (i.e. those with a worker caste) provide highly informative systems in this context because reproductive forms (queens and reproductive workers) exhibit unusual features such as extended longevities and positive relationships between fecundity and longevity. This thesis therefore presents a set of experiments using the eusocial bumblebee Bombus terrestris to elucidate the relationship between sociality and ageing. B. terrestris is especially suited to this goal because workers can be reproductive depending on social context and reproductive workers exhibit a condition-dependent positive fecundity-longevity relationship. An experiment to test the hypothesis that greater larval nutrition leads to high-quality adult workers able to express this relationship revealed, as predicted, significantly positive associations between body size, reproductivity and longevity, with larval nutrition affecting worker quality via its positive connection to adult body size. A reciprocal transfer experiment to test the relative influence of individual and social factors on ageing and longevity in social organisms simultaneously at the phenotypic and transcriptomic (gene expression) level revealed workers' longevity and age-related gene expression were affected in a similar manner by an interaction of individual and social factors. A novel phenomenon uncovered by this thesis was within-colony, within-cohort multimodality in the frequency distribution of worker longevity. An experiment showed that isolated workers did not express such multimodality, supporting the role of social factors in longevity determination in this context. It also showed that, surprisingly, isolation significantly increased worker longevity, possibly connected to workers' reproductivity. Lastly, RNA sequencing suggested that, as predicted, the molecular basis of ageing differs between reproductive and non-reproductive workers, and characterized the gene expression changes associated with workers becoming egg-layers. In sum, this thesis helps provide new understanding of how social evolution affects the evolution of ageing and longevity.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Chris White
Date Deposited:	01 Dec 2025 13:46
Last Modified:	01 Dec 2025 13:46
URI:	https://ueaeprints.uea.ac.uk/id/eprint/101166
DOI:

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