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Genetics of polymorphism in the wood tiger moth

Supervisor: Prof. Chris Jiggins

Project summary:

The project will identify the genomic locus controlling wing pattern polymorphism in the garden tiger moth and study the genetic origins of this pattern variants. A genome sequence is already available for the species, and we have also obtained genome sequences for individuals sampled from a polymorphic population in Finland. In addition to identifying genotypic differences within the Finnish population, additional sequences could be obtained to analyse population genomic variation across its geographic distribution in the northern hemisphere. In particular, populations from Scotland where all morphs are yellow, as well as from populations in Georgia where unusual red morphs exist. Additional species in the genus Arctia also show pattern polymorphism and an additional project could look at the origins of variants across related species.

The study of warningly coloured butterflies and moths has long fascinated evolutionary biologists, especially those with pattern polymorphism. Recent work has shown that polymorphisms often have a relatively simple genetic control and alleles are commonly associated with inversions, which act to reduce recombination around functional genes. Such systems therefore upper an opportunity to understand how novel patterns arise and are maintained in the genome, and the role of recombination in The aposematic wood tiger moth (Arctia plantaginis; formerly Parasemia plantaginis) uses bright wing patterning to signal its unpalatability to visual, avian predators. Males exhibit a hindwing colour polymorphism, with existence of yellow and white morphs in Finland. These colour morphs occur at varying frequencies and appear to be maintained under frequency-dependent selection, and have been studied extensively in the field and laboratory. It has been suggested that two or more linked genes underlie this polymorphism, although this remains untested. This is therefore an excellent system for studying the origins and maintenance of genetic variation within populations.

What the student will be doing:

You will analyse genome sequences and call variants among populations. These genomic data will be analysed for association between genetic variants and wing pattern variation. You will analyse regions of association to search for candidate genes and analyse patterns of expression. One approach would be in situ hybridisation to identify whether potential candidate genes are expressed differentially within polymorphic regions of male hindwings during development. In addition, any potentially linked genes such as for behavioural or chemical traits could also be investigated. Finally if clear candidate genes emerge it will be possible to carry out functional studies using CRISPR.

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 Mappes and her group in Finland the student will also learn field techniques and the biology of this species.

References:

Hegna RH, Galarza JA & Mappes J 2015: Global phylogeography and geographical variation in warning coloration of the wood tiger moth (Parasemia plantaginis). Journal of Biogeography 42 (8), 1469-1481.

Joron, M. et al. Chromosomal rearrangements maintain a polymorphic supergene controlling butterfly mimicry. Nature 477, 203–206 (2011).

Kunte, K. et al. doublesex is a mimicry supergene. Nature 507, 229–232 (2014).