Reproductive plasticity and the evolution of the insect societies

A fundamental goal of evolutionary biology is to understand how novel traits arise. Eusociality represents an extreme form of social organization which has evolved independently a number of times across insects and is characterized especially in the Hymenoptera by a novel polyphenism between reproductive (queen) and non-reproductive (worker) castes. While a growing body of research continues to improve our understanding of the mechanisms underlying the development of these castes, less is known about how castes evolved from solitary ancestors. In this dissertation, I leverage naturally-occurring social plasticity in two species of bees to shed light on potential mechanisms of caste evolution across social insects. In Chapter 1, I provide a detailed overview of the work contained within this dissertation. In Chapter 2, I develop a perspective on how ancestral behavioral plasticity may have facilitated the evolution of castes through genetic accommodation. In Chapter 3, I present a de novo transcriptome assembly for Megalopta genalis, a facultatively eusocial sweat bee that exhibits multiple social phenotypes within one population and may therefore represent a transition between solitary and social reproduction. I use this transcriptome in Chapter 4 to identify gene expression differences associated with social phenotypes of M. genalis, and compare these to genes involved in caste determination of other eusocial species as well as genes implicated in the evolution of eusociality through comparative studies of bees. In Chapter 5, I use a high-resolution behavioral tracking system to discover a previously undescribed form of colony organization in honey bees that occurs after a colony loses and is unable to replace its queen and some workers begin to lay eggs. Surprisingly similar to the social variation observed across nests of M. genalis, these colonies of honey bee workers display multiple levels of social plasticity, evoking transitional stages in eusocial evolution associated with the venerable Ovarian Ground Plan Hypothesis. Finally, in Chapter 6, I use transcriptomics and chromatin accessibility analyses of bees in laying worker colonies to explore how changes in brain gene regulation may contribute to variation in colony social organization, with comparative analyses to place this variation in the broader context of caste evolution across social insect lineages.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Ecol, Evol, Conservation Biol

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2019

Author dc:creator

• Jones, Beryl M.

Contributors dc:contributor

• Robinson, Gene E.
• Bell, Alison M.
• Hudson, Matthew E.
• Suarez, Andrew V.

• social insects
• social plasticity
• caste evolution
• phenotypic plasticity
• gene regulation
• Apis mellifera
• Megalopta genalis

Statement dc:rights

• Copyright 2019 Beryl Jones

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/105141

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/105141