Abstract
dc:description.abstractInsect chemical profiles are diverse and complex, reflecting the wide range of functions they serve. Volatile compounds are used in foraging, defence, and mating, and pheromones are particularly important to the lives of insects. These are chemical signals that mediate the behaviour of conspecifics. Chemical profiles therefore vary according to the ecological roles of their constituent compounds, as well as their evolutionary histories and adaptive values. Studying this variation can shed light on the processes driving insect chemistry evolution. Neotropical butterfly chemical profiles are highly variable between species, sexes, and even tissues of the same individual. These butterflies are chemically defended and advertise toxicity with brightly coloured, mimetic warning signals. In addition, sex pheromones play a crucial role in butterfly mate detection, attraction, and assessment. In this thesis, I investigate the evolutionary mechanisms that shape butterfly scent chemistry. First, I assess the influence of mimicry and phylogeny on chemical profile variation in mimetic heliconiine and ithomiine butterflies. I show that chemical signal similarities among species are most likely the product of shared ancestry, rather than convergence for chemical mimicry. This suggests chemical signals in these groups are primarily used for intraspecific communication. Next, I examine the underlying mechanisms that drive the persistence, loss, and modification of a chemical signalling trait among Heliconiini species. I show that this trait arose ancestrally via relaxation of selection, and has been lost multiple times, at least once through an intensification of positive selection. In addition, I show this trait does not have the same function in two distantly related species, suggesting trait function may be tied to trait value. Finally, I identify candidate pheromone compounds in H. erato. I find that a synthetic blend of the most common compounds found in the male clasper scent gland reduces male courtship when applied to unmated females. However, electrophysiologically active components do not produce the same response, suggesting the antiaphrodisiac response in H. erato is not straightforward. The work presented here contributes to our understanding of the evolution of butterfly scent chemistry. A mixture of results from evolutionary reconstructions, phylogenetic analyses, and functional manipulation experiments highlight the importance of several evolutionary processes in the production of a complex trait.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2023
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Blow, Rachel
- Advisor dc:contributor.advisor
-
- Jiggins, Chris
Subjects
dc:subject × 6Rights
dc:rightsIdentifiers
dc:identifier.*- DOI dc:identifier.doi
- https://doi.org/10.17863/CAM.111726
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/373191