Mimicry: developmental genes that contribute to speciation.

Area of Science:

• Evolutionary Biology
• Genetics
• Speciation Research

Background:

• The genetic and developmental underpinnings of speciation are not fully understood, despite the recognized role of natural selection.
• Müllerian mimicry in Heliconius butterflies is a key example of recent speciation.
• Understanding the genetic basis of mimetic shifts is crucial for explaining species formation.

Purpose of the Study:

• To investigate the genetic architecture of Müllerian mimicry in the sister species Heliconius cydno and Heliconius melpomene.
• To identify the genetic loci and interactions controlling mimetic patterns and their role in reproductive isolation.

Main Methods:

• Genetic analysis of Müllerian mimicry in Heliconius cydno and H. melpomene.
• Identification of autosomal loci controlling color pattern.
• Investigation of dominance, epistasis, and linkage effects.

Main Results:

• Ten autosomal loci were identified, with half having major effects on mimicry.
• Eight loci are homologous to genes controlling pattern differences within species.
• Dominance is influenced by modifier loci, and epistasis occurs at multiple levels.
• Loci cluster into two genomic regions ('supergenes'), suggesting constraints on color pattern evolution.
• Mimicry acts as a barrier to gene flow, but introgression occurs in unlinked regions.

Conclusions:

• Natural selection is a powerful force in speciation, driving mimetic shifts and reproductive isolation.
• Genetic factors like linkage, modifiers, and epistasis shape the strength of mimicry as a speciation barrier.
• Different genetic architectures can achieve similar mimetic patterns, indicating limited developmental constraints.