Speciation genomics of eye size variation in Heliconius butterflies

• Applicant: Professor Richard Merrill, Ph.D.
• Subject Area: Evolution, Anthropology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 554326224

Adaptation to different ecological niches can result in the evolution of new species, and a major goal of evolutionary biology is to identify the genetic changes underlying population divergence and speciation. Both visual ecology, the study of how animals use visual systems to meet their ecological needs, and speciation genomics, which concerns itself with how genomic variation both within and between species changes over evolutionary timescales, are now mature fields of research. However, beyond a few notable exceptions, largely relating to adaptation in aquatic environments, there has been relatively little interplay between these fields. Our research will address the evolution and genomic basis of eye size variation in insects. Highly visual Heliconius butterflies are one of only a few groups in which it will be possible to achieve an integrated understanding of visual adaptation. This Neotropical genus is well known for its bright warning patterns, which are also used as mating cues, and has been especially well studied with respect to adaptation and speciation. Our preliminary work has revealed divergence in eye morphology both within and between Heliconius species and quantitative genetic analyses imply that these differences are driven by selection. The major objective of the project is to understand the molecular basis and evolution of this variation, and how it may pose a barrier to gene flow during population divergence. We will first establish patterns of eye morphology evolution across the ‘Heliconius melpomene-silvaniform’ group species. We will then characterise variation in eye size across an elevational gradient, and in particular test for parallel evolution at both organismic and molecular levels (using a GWAS approach). Finally, we will identify genomic regions associated with between species shifts in eye morphology with QTL mapping, and using state-of-the-art population genomic methods determine whether these relate to genomic regions of reduced local gene flow. This work will offer new insights into speciation, a process fundamental to evolution and biodiversity, but also has wider implications for our understanding of the genetics of a key ecologically relevant sensory phenotype.

• DFG Programme: Research Grants