Rapid diversification and wing colour pattern evolution in tropical butterflies

The formation of new species is a major topic in evolutionary biology. Both the drivers of diversification in certain lineages and the genetic architecture underlying phenotypic differentiation are studied intensively across the field. Certain diverse groups of co-localizing toxic butterflies form mimicry rings of similarly looking species, influenced by the selective forces of predation and aposematism. Mimicry rings form an excellent system for studying phenotypic change and convergence, since often several subspecies with different wing colour patterns exist within one species, and different species exhibit convergent changes in phenotypes. Ithomiini butterflies and Heliconius are classic examples of rapidly radiating Neotropical butterfly genera participating in these mimicry rings. Such recent and rapid adaptive radiations are ideal systems for addressing how new species arise because they may preserve key morphological and ecological adaptations associated with speciation. My PhD investigates phylogeographic relationships and patterns of hybridisation in three ithomiine genera: Melinaea (chapter 2), Mechanitis (chapter 2) and Ithomia (chapter 5). I also study the genetic architecture underlying wing pattern divergence in these genera (chapter 3-5) and in Heliconius (chapter 4), to elucidate the genomic changes that control morphological variation. Chapter 1 is a general introduction to the questions and the study system. Chapter 2 resolves the phylogeny of Melinaea and Mechanitis, and explores potential drivers of rapid diversification through whole genome resequencing of most (sub)species covering a wide geographic range. Chapter 3 focuses on colour pattern evolution in one species per genus, through genome-wide association studies in several convergent phenotype switches. Chapter 4 characterises the genes identified in chapter 3 through CRISPR-Cas9, in situ hybridisation and antibody staining. This chapter focuses on Mechanitis messenoides, but also contains work performed in Melinaea and Heliconius, all exploring the same colour loci. Chapter 5 studies the phylogeny of Ithomia, which has diversified slower than Melinaea and Mechanitis. Specifically, I investigated patterns of hybridisation and chromosomal rearrangements, and I examined wing colour pattern evolution in Ithomia salapia. Chapter 6 is a discussion of all the work in this thesis. I combined a variety of methods, ranging from fieldwork to population genomics analyses, phylogenetics and genome-wide association studies, to functional genetics such as CRISPR-Cas9 genetic modification, RNAseq, in situ hybridization and antibody staining. I resolve the classification of these notoriously taxonomically challenging butterflies, and I find that hybridisation and biogeography may have played a role in the fast diversification of Melinaea and Mechanitis. Moreover, I show that the highly convergent wing colour patterns across several ithomiine genera are due to regulatory changes at the same wing colour pattern genes that have also been identified in Heliconius.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Van Der Heijden, Eva

Advisors dc:contributor.advisor

• Meier, Joana
• Jiggins, Chris

• biodiversity
• colouration
• evolution
• speciation

Licence

• https://www.repository.cam.ac.uk/bitstreams/6d893ddb-8ef8-43e9-9533-4181dd951571/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.123865

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/393573