Tigermoth polymorphism

How variation is maintained has been a long-discussed question in evolutionary biology. In many cases there is not one single genetic variant to optimise fitness. We explore possible mechanisms by studying colour variation in the wood tiger moth Arctia plantaginis. Males of this species show a polymorphism (white or yellow) in hindwing colour, which is controlled by a single locus with two alleles, dominant white and recessive yellow.  Previous work has identified the responsible gene for white colour and shown that it resulted from a duplication of the yellow-e gene.  The species uses hindwing colour as a warning signal in combination with chemical defences. Naïve predators learn to associate the warning coloration with unpalatability and avoid similar morphs in the future resulting in a strong advantage for the more common form. The maintenance of polymorphic populations consisting of both, yellow and white forms, over many years is thus puzzling. We explore potential mechanisms such as trait correlations, which can lead to genetic trade-offs if an increase in one fitness component incurs a cost in another. For example, one form might have a more efficient warning signal or chemical defence potentially at the expense of reduced mating success or fecundity.

In close collaboration with Johanna Mappes’ group at the University of Helsinki we use genomic approaches as well as classical quantitative genetic methods to investigate the genetic basis of life-history traits in this species and their relationship with the colour locus to address the following questions:

• Are there differences between white and yellow morphs beyond hindwing colouration?
• What is the genetic architecture of traits in general? Is some of the observed phenotypic variation genetic and do different traits share parts of their genetic basis?
• Where are the genetic loci responsible for trait variation located in the genome? Are they close or within the region of the hindwing colour locus?

Publications:

Brien, M. N., Orteu, A., Yen, E. C., Galarza, J. A., Kirvesoja, J., Pakkanen, H., ... & Mappes, J. (2023). Colour polymorphism associated with a gene duplication in male wood tiger moths. Elife, 12, e80116.

Yen, E. C., McCarthy, S. A., Galarza, J. A., Generalovic, T. N., Pelan, S., Nguyen, P., ... & Jiggins, C. D. (2020). A haplotype-resolved, de novo genome assembly for the wood tiger moth (Arctia plantaginis) through trio binning. GigaScience, 9(8), giaa088.