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The smell of speciation-chemical signalling in butterfly diversification

Supervisor: Prof. Chris Jiggins

Project summary:

This project will study the genetic basis for pheromone differences between species and the corresponding female preferences for those differences. The work will involve analysis of crossing experiments combined with genomic and chemical analysis will be used to carry out Quantitative Trait Locus analysis of differences in pheromones between H. melpomene and H. cydno. Genetic analysis will be complemented by behavioural assays to study the role of specific compounds in mating behaviour. We already have electrophysiological evidence for the role on one key compound in mate choice and this work will follow up to try and understand what the information is being conveyed by these signals and how they are interpreted by females.

Speciation is the fundamental process that underlies the biodiversity of our plant, and despite a wealth of recent theoretical and empirical advances, there is much we still do not understand. The Heliconius butterflies offer an excellent opportunity to gain insights into the genetic architecture of speciation and its genomic consequences, by integrating genomic data with ecological and behavioural processes that underlie speciation in this group. The wing patterns of this group are particularly well studied, but in contrast we know less about chemical communication, which also plays an important role in sexual communication and species recognition. Nonetheless, we have over recent years identified a key compound involved in sexual signalling in H. melpomene, and carried out crosses to study the genetic basis for the production of these compounds. We are therefore well placed to follow up on our understanding of the genetic basis for pheromonal differences between species.

What the student will be doing:

You will design experiments to follow up on QTL analysis of pheromone differences between species that are currently underway. This may involve raising more controlled crosses between H. melpomene and H. cydno in panama and collecting chemical samples from the wings of hybrid butterflies. These samples will be analysed in the laboratory of our collaborator in Germany, Stefan Schulz. If the resolution of mapping experiments is sufficient to identify candidate genes you could also carry out genetic manipulation experiments using CRISPR to test the function of candidate wing pheromone genes, and conduct behavioural experiments with resulting mutants. You will also carry out behavioural trials to study the genetic basis of preference behaviours. You will use synthesised compounds to study the function of specific compounds in butterfly courtship, mating and species recognition.

The student will learn genomic techniques for analysis of large sequence data sets and comparative analysis of genome sequences. In addition the student will learn about the application of CRISPR in insects for studying the function of evolutionarily relevant genes. In collaboration with Prof Schultz the student will also learn about the biochemistry of volatile chemical signals. The student will also learn about tropical ecology more broadly and the study of insects in the tropics.

References:

Darragh, K. et al. Male sex pheromone components in Heliconius butterflies released by the androconia affect female choice. PeerJ 5, e3953 (2017).

Mann, F. et al. The Scent Chemistry of Heliconius Wing Androconia. J. Chem. Ecol. 43, 843–857 (2017). 

Merrill, R. M. et al. The diversification of Heliconius butterflies: What have we learned in 150 years? J. Evol. Biol. (2015). doi:10.1111/jeb.12672