The molecular mechanisms of behavioural transitions in insect life-cycles

Abstract

Phenotypic plasticity is one of the most important fundamental processes by which organisms adapt to changes in their environment. Alternative behavioural phenotypes emerge via the expression of shared genes from the same genome. These phenotypes are expressed at different stages of key life-history transitions, or when organisms perform distinct tasks as they shift flexibly from one behavioural state to another through their breeding cycle. Here, I investigate the molecular mechanisms underpinning plasticity in three types of phenotypic transitions: a key life-history transition (transition from worker to queen, in the social wasp Polistes lanio), an evolutionary transition (how non-social ancestral behaviours may provide a mechanistic ground plan for the origins of division of labour and caste evolution in the social Hymenoptera, using the non-social wasp Ammophila pubescens), and a series of behavioural transitions through a nesting cycle (behavioural phases exhibited by A. pubescens during the nesting cycle). Finally, plastic phenotypes can arise when populations become isolated (e.g. due to habitat fragmentation) forcing them to exploit different resources; in my final chapter, I examine the genetic diversity and differentiation of A. pubescens across a fragmented landscape. My results show that key life-history transitions are characterised by distinct “transitional” molecular signatures. Second, I found evidence that cycles of reproductive and provisioning behaviours may provide a mechanistic ground plan for the evolution of sociality. Third, I found that behavioural phases of the non-social wasp nesting cycles are defined by distinct molecular signatures during the provisioning phases, but otherwise very subtle molecular signatures for the other phases. Finally, I found little evidence of genetic differentiation in populations of A. pubescens. In conclusion, phenotypic transitions are not only underpinned by simple shifts between molecular processes but also by elaborated changes in genomic signatures allowing organisms to adjust their behaviours responsively to their environments.

Date of Award	24 Mar 2020
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Jane Memmott (Supervisor) & Seirian R Sumner (Supervisor)