Heliconius species are known for abundant examples of wing pattern divergences and mimicry among species. The genus Heliconius is a recently diverged radiation and includes species in a variety of phases of speciation, and hybridization commonly occurs between taxa. Heliconius cydno has a strikingly distinct wing pattern from is closest sister species H. pachinus. Researchers at the University of Chicago (Konforst et al. 2013) found by comparing full genomes that these species, which are inter-fertile and sympatric, hybridize to the point that gene flow makes them almost entirely genetically identical. This homogenization of the genomes allows for easy identification of just 12 small regions where there is significant genetic diversity, two thirds of which are known to be involved in the determination of wing pattern elements. These distinct alleles are selected for in the geographic region in which they originally appear because of their advantages for mating and avoiding predation, and the researchers of this study use it as an example indicating that mimicry may have a rich role in genetic evolution.
Over evolutionary time the behavioral and species barrier determined by these few genetic differences lead to broader build up of genome-wide divergence between the species, and again the Heliconius system allowed this research group a clear look at how genetic divergence evolves subsequent to initial speciation by comparing cydno and pachinus with a increasingly more divergent races of a third, slightly more distant species, H. melpomene. An exponential increase in genetic difference over time indicates that divergence after the speciation event may be a result of divergent and purifying selection. The Heliconius model further allows analysis of the targets of and processes contributing to divergent selection, and is a starting place for examining how general these phenomena may be in speciation in other systems (Kronforst et al. 2013)
- Kronforst, M.R.; M.E.B. Hansen, N.G. Crawford, J.R. Gallant, W. Zhang, R.J. Kulathinal, D.D. Kapan, S.P. Mullen, 2013. Hybridization Reveals the Evolving Genomic Architecture of Speciation. Cell Reports October 31, 2013 DOI: 10.1016/j.celrep.2013.09.042. Available online: http://download.cell.com/cell-reports/pdf/PIIS2211124713005652.pdf?intermediate=true.
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