Date of Award:

12-2025

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Karen Kapheim

Committee

Karen Kapheim

Committee

Susannah French

Committee

Robert Schaeffer

Abstract

Organisms face many trade-offs in how to invest in these traits. One example is the trade-off between reproduction and longevity. Queens of social insects seem to escape this trade-off, producing thousands of eggs daily, despite having a longer lifespan than their workers. Some hypotheses have been proposed to explain this phenomenon, such as an evolutionary change in the molecular pathways that regulate queen investment in maintenance, growth, and reproduction. An alternative hypothesis suggests that the tradeoffs are rarely observed in queens due to the extensive resources provided by the help of workers. While these hypotheses have supporting evidence, they have only been tested in highly social species in which queens are unable to live independently of their workers.

Megalopta genalis is a facultative eusocial bee exhibiting one of two reproductive strategies: the social and solitary. We tested the molecular rewiring hypothesis and the access to resources hypothesis in foundresses of Megalopta genalis. We compared the gene expression in the fat body, oxidative stress, and reproductive anatomy between queens and solitary foundresses before and after offspring emergence. We experimentally removed workers from a group of queens and compared them to control queens who kept their workers.

Our results indicate that queens had larger oocytes than females in the other treatments and also exhibited the most significant shift in gene expression, with 660 differentially expressed genes compared to pre-emergence foundresses. Solitary females did not exhibit a similar shift in gene expression, with only 33 genes differentially expressed compared to pre-emergence foundresses. These results support the access to resources hypothesis. Only eight genes were differentially expressed between queens whose workers were experimentally removed and pre-emergence foundresses, indicating that these genes are sensitive to changes in the social environment. We did not detect any genes that were differentially expressed between social and solitary foundresses before their offspring emerged, as would be expected with the molecular rewiring hypothesis. We did not identify any significant differences in oxidative stress among the nest foundresses. Our results support the hypothesis that queens evade the trade-off between longevity and fecundity by accessing resources provided by workers.

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