BRS Chris Jiggins: The structure of genomes and the origins of biodiversity

host: Dolph Schluter

Title talk: The structure of genomes and the origins of biodiversity 

Abstract: There is considerable interest in the role of structural genomic variation in evolution. This dimension of genomic variation is becoming increasingly accessible due to the availability of long read sequencing, and it is clear that duplications and insertions can play an important role in adaptation.  We have identified several cases in which phenotypic variants turn out to be controlled by such large scale structural mutations. Wing colour patterns in Lepidoptera have long been an exemplar system for studying adaptive evolution, and we have shown that TE insertions influencing regulatory variation have been responsible for adaptive change in both Heliconius and Hypolimnas butterflies. In H. erato we could verify the adaptive role of a TE insertion by CRISPR recapitulation of the natural mutation. In Hypolimnas the mutation caused a reversion of phenotype to an ancestral form, which was mimetic to a toxic model species, Danaus chrysippus. In contrast, in the wood tiger moth, we have shown that a gene duplication was responsible for a wing pattern polymorphism, with an additional copy of a yellow family gene, which we named valkea, being responsible for a male-limited wing polymorphism. Finally, I will present evidence for introgression of structural variants in both directions between two crop pest species, Helicoverpa armigera and H. zea, which hybridise in Brazil. A cluster of trypsin repeats involved in resistance to Bt toxins has introgressed into H. armigera, potentially threatening GM soybean and other crops in Brazil, while a chimeric gene conferring pyrethroid insecticide resistance has introgressed in the opposite direction. We have also been working on large scale chromosomal evolution in groups of rapidly radiating ithomiine butterflies. Despite a backdrop of conserved chromosome structure in Lepidoptera, two clades that have rapidly radiated, Mechanitis and Melinaea, also show remarkably high rates of chromosomal rearrangements. It remains unclear the direction of causality between these chromosomal changes and high rates of speciation. These examples demonstrate that gene duplications, TEs and chromosomal rearrangements are common mechanisms for recent adaptive evolution.

Short biography: Chris Jiggins is Professor of Evolutionary Biology at the University of Cambridge and has expertise in insect genomics and studies of adaptation. His work has led the rise of Heliconius butterflies to become a textbook example of ecological adaptation and the origin of new species. He has used genomics to study genes under selection in a variety of insect species and was recently elected a Fellow of the Royal Society