Insights into the Evolution of Moth Pheromone Communication: Lessons from the European Corn Borer
Author
Summary, in English
Chemical communication by means of sex pheromones is central to the mating systems of a wide range of
organisms. Because reproductive isolation is often based on pheromone differences, understanding how
pheromones diverge is necessary for a complete comprehension of the speciation process. Moths (Insecta:
Lepidoptera) contributes highly relevant examples to the theory of speciation because subtle chemical changes
in their sex pheromones may often be the initial triggers for population divergence, and lead to reproductive
isolation. Over the years, the European corn borer Ostrinia nubilalis and its congeners have become a model
system for investigating the genetics of pheromone communication systems and the role of sexual signals in
speciation. The Ostrinia system has received a lot of attention because of the naturally-occurring pheromone
polymorphism, and the relatively simple nature of the pheromone components which seemed amenable to a
reductionistic approach. The system has turned out to be surprisingly complex, because the genetic bases for
pheromone production by females, chemosensory responses by males, and behavioural responses by males have
been shown to be different.
In this thesis, I report on advances made on several fronts of the Ostrinia communication system. To
summarize, I describe the identification of the enzyme-encoding gene pgFAR which is responsible for
phenotypic variation in female pheromone production among O. nubilalis and allied species. The pgFAR gene
encodes a Lepidoptera-specific fatty acyl-CoA reductase that catalyzes the NADPH-dependent reduction of fatty
acyl substrates during the pheromone biosynthesis. I could show that (i) structural variation in the coding region
of the protein is tightly associated with variation in the substrate preference of the enzyme, (ii) the ratio of
pheromone components used by O. nubilalis and its congeners is modulated by the pgFAR activity, (iii) the
pgFAR gene experience positive Darwinian selection, and (iv) mutational changes at sites under selection cause
both gradual or saltational shift in the enzyme activity. I also explored whether pheromone-specific olfactory
receptors expressed on male antenna are candidate barrier genes involved in the differentiation between the
pheromone races of O. nubilalis. I found evidence that three sex-linked loci are under selection and well
associated with genetic differentiation between the races, suggesting that these genes are good candidate barriergenes
worth considering for measuring natural selection in the wild. Finally, I document the role played by a
male courtship pheromone in mate choice, and its implication on the evolution of female pheromone as a
consequence of gene sharing.
organisms. Because reproductive isolation is often based on pheromone differences, understanding how
pheromones diverge is necessary for a complete comprehension of the speciation process. Moths (Insecta:
Lepidoptera) contributes highly relevant examples to the theory of speciation because subtle chemical changes
in their sex pheromones may often be the initial triggers for population divergence, and lead to reproductive
isolation. Over the years, the European corn borer Ostrinia nubilalis and its congeners have become a model
system for investigating the genetics of pheromone communication systems and the role of sexual signals in
speciation. The Ostrinia system has received a lot of attention because of the naturally-occurring pheromone
polymorphism, and the relatively simple nature of the pheromone components which seemed amenable to a
reductionistic approach. The system has turned out to be surprisingly complex, because the genetic bases for
pheromone production by females, chemosensory responses by males, and behavioural responses by males have
been shown to be different.
In this thesis, I report on advances made on several fronts of the Ostrinia communication system. To
summarize, I describe the identification of the enzyme-encoding gene pgFAR which is responsible for
phenotypic variation in female pheromone production among O. nubilalis and allied species. The pgFAR gene
encodes a Lepidoptera-specific fatty acyl-CoA reductase that catalyzes the NADPH-dependent reduction of fatty
acyl substrates during the pheromone biosynthesis. I could show that (i) structural variation in the coding region
of the protein is tightly associated with variation in the substrate preference of the enzyme, (ii) the ratio of
pheromone components used by O. nubilalis and its congeners is modulated by the pgFAR activity, (iii) the
pgFAR gene experience positive Darwinian selection, and (iv) mutational changes at sites under selection cause
both gradual or saltational shift in the enzyme activity. I also explored whether pheromone-specific olfactory
receptors expressed on male antenna are candidate barrier genes involved in the differentiation between the
pheromone races of O. nubilalis. I found evidence that three sex-linked loci are under selection and well
associated with genetic differentiation between the races, suggesting that these genes are good candidate barriergenes
worth considering for measuring natural selection in the wild. Finally, I document the role played by a
male courtship pheromone in mate choice, and its implication on the evolution of female pheromone as a
consequence of gene sharing.
Department/s
Publishing year
2010
Language
English
Document type
Dissertation
Publisher
Chemical Ecology and Ecotoxicology, Department of Biology, Lund University
Topic
- Ecology
- Biological Sciences
Keywords
- biosynthetic enzymes
- evolution
- Ostrinia nubilalis
- mate choice
- mate finding
- olfaction
- biosynthesis
- speciation
- moth
- pheromone
- olfactory receptors.
Status
Published
Project
- Evolutionary mechanisms of pheromone divergence in Lepidoptera
Research group
- Pheromone Group
Supervisor
ISBN/ISSN/Other
- ISBN: 978-91-7473-022-7
Defence date
1 October 2010
Defence time
10:00
Defence place
Blå Hallen, Ekologihuset
Opponent
- James Mallet (Professor)