Journal Update 4: Contrasting genomic and phenotypic outcomes of hybridization between pairs of mimetic butterfly taxa across a suture zone

In this study, researchers use reduced-complexity genomic data to compare phenotypes, genetic structure and hybridization patterns of two mimetic butterfly species, Ithomia salapia and Oleria onega. Müllerian mimicry in butterflies describes a defense mechanism where multiple species converge locally on warning wing colour patterns and form mimicry “rings”. Since nonmimetic butterflies can go through more intense selective pressure due to predation risk, mimicry can be seen as a strong ecological driver of speciation and could potentially have triggered the diversification of large radiations of mimetic butterflies.
 

Using a genotyping by sequence approach to generate genetic data and analyzing over 30000 SNPs, the researchers finds that there are significant genotypic as well as phenotypic difference between the 2 species. For the 2 I. salapia lineages analyzed,  the results show that they seem to hybridize only rarely (shown as a in figure above). On the other hand, hybrids are not only more commonly found in O. onega, they are also genetically and phenotypically more variable (shown as b).  

Admixture mapping analysis shows that a small percentage of SNPs analyzed are associated with colour pattern variation in I. salapia (0.49%) and in O. onega ( 0.69%). However, these loci are normally represented among the candidate barrier loci. The researchers suggest that this result might imply other genetic mechanisms could play an important role in the hybridization and and variations observed. 

Gauthier, J., de Silva, D.L., Gompert, Z., Whibley, A., Houssin, C., Le Poul, Y., McClure, M., Lemaitre, C., Legeai, F., Mallet, J. and Elias, M., 2020. Contrasting genomic and phenotypic outcomes of hybridization between pairs of mimetic butterfly taxa across a suture zone. Molecular Ecology.

Molecular Ecology

Monica Cheung– April 29, 2020