Molecular mechanism and evolutionary process underlying female-limited batesian mimicry in papilio polytes

Abstract

Mimicry is an important evolutionary trait involved in prey-predator interactions. In a swallowtail butterfly Papilio polytes, only mimetic-form females mimic the unpalatable butterfly, Pachliopta aristolochiae, but it remains unclear how this female-limited polymorphic Batesian mimicry is generated and maintained. To explore the molecular mechanisms, we determined two whole genome sequences of P. polytes and its related species P. xuthus for comparison. The genome projects revealed a single long-autosomal inversion outside doublesex (dsx) between mimetic (H) and non-mimetic (h) chromosomes (Chr25) in P. polytes. The inversion site was just same as the mimicry locus H identified by linkage mapping. The gene synteny around dsx among Lepidoptera suggests that Hchromosome originates from h-chromosome. The 130 kb inverted region includes three genes, doublesex (dsx), UXT, and U3X, all of which were expressed from Hchromosome, but rarely from h-chromosome, indicating that these genes in Hchromosome are involved in the mimetic trait as supergene. Amino acid sequences of Dsx were substituted at over 13 sites between H- and h-chromosomes. To certify the functional difference of Dsx, we performed electroporation-mediated knockdown and found that only female dsx from H-chromosome (dsx_H) induced mimetic patterns but simultaneously repressed non-mimetic patterns on female wings. We propose that dsx_H switches the coloration of predetermined patterns in female wings and that female-limited polymorphism is tightly kept by chromosomal inversion. In this chapter, I will introduce the above results and discuss about the molecular mechanism and evolutionary process underlying the female-limited Batesian mimicry in P. polytes.