A shared gene but distinct dynamics regulate mimicry polymorphisms in closely related species

Area of Science:

• Evolutionary genetics
• Developmental biology
• Animal coloration

Background:

• Sex-limited polymorphisms, like female butterfly mimicry, are common and adaptive but their genetic basis is poorly understood.
• Papilio butterflies exhibit female-limited mimicry polymorphism, with distinct mimetic and non-mimetic wing patterns.
• The doublesex (dsx) gene is implicated in controlling these alternative female color patterns.

Purpose of the Study:

• To investigate the molecular and developmental genetic basis of female-limited mimicry polymorphism in Papilio butterflies.
• To determine the role of doublesex (dsx) in controlling sexual dimorphism and mimicry.
• To identify downstream genes and compare the genetic mechanisms underlying mimicry evolution across species.

Main Methods:

• RNA sequencing (RNA-seq) was performed on Papilio lowii females.
• dsx gene expression was experimentally manipulated (knockdown) in several Papilio species.
• Gene expression data were compared between P. lowii and previously studied P. alphenor.

Main Results:

• Knockdown of dsx expression in females resulted in male-like color patterns, confirming dsx's role in both sexual dimorphism and polymorphism.
• Alleles of dsx exhibit unique spatiotemporal expression patterns in mimetic females of P. lowii and P. alphenor.
• While some wing patterning genes are differentially expressed in both species, their temporal expression patterns differ significantly.

Conclusions:

• The doublesex (dsx) gene is a key regulator of mimicry polymorphism in Papilio butterflies.
• Despite the conserved role of dsx, the downstream genetic pathways driving mimicry evolution are distinct between closely related species.
• This highlights divergent evolutionary mechanisms underlying a shared phenotypic trait.