The evolution and divergence of the special homeobox genes in Pararge aegeria

Paralogs arise through gene duplications and their subsequent divergence provides the raw material for functional innovation. Although this has been inferred from studies on interspecific sequence variation in paralogs, not much is known about standing intraspecific paralog variation and associated phenotypic variability. Paralogs in the Hox cluster are rare, but the so called paralogy group 3 (PG3) has undergone independent tandem duplications in several insect clades. Within the ditrysia, a derived clade of the Lepidoptera, duplications in the ancestral PG3 gene zerknullt (zen) resulted in 4 so-called special homeobox genes (Shx). It has recently been shown that there is significant interspecific variation in these Shx paralogous genes. Sequencing of the Shx genes within my model species, the Speckled Wood butterfly Pararge aegeria, has revealed that although intraspecific variation is lower than interspecific variation, it is very high for a Hox (-derived) gene. To investigate this in more depth, I sequenced the four Shx genes, zen, wingless and the cytochrome oxidase I subunit in 25 populations of P. aegeria spanning from N. Africa to Scandinavia. Preliminary results show the presence of population specific variants, even within the highly conserved homeobox region of one of the Shx paralogs. This suggests possible local adaptation events in response to different selection pressures.