Interplay between Developmental Flexibility and Determinism in the Evolution of Mimetic Heliconius Wing Patterns

Area of Science:

• Evolutionary Biology
• Developmental Genetics
• Molecular Biology

Background:

• Müllerian mimicry in Heliconius butterflies offers natural experiments to study evolutionary predictability.
• Wing pattern diversity in this group is extensive, with mimicry evolving recently (2.5-4.5 Ma).
• WntA is a key signaling ligand and a major locus influencing wing pattern variation.

Purpose of the Study:

• To investigate the role of WntA in generating mimetic wing patterns in Heliconius butterflies.
• To test whether genetic architectures and developmental processes canalize evolution towards predictable outcomes.
• To explore if historical contingencies lead to alternative evolutionary pathways for similar challenges.

Main Methods:

• CRISPR/Cas9 targeted mutagenesis was used to create WntA-deficient wings.
• Experiments were conducted on 12 species and 10 intraspecific variants, including co-mimetic pairs.
• Effects of WntA knockouts on wing pattern and scale cell types were analyzed.

Main Results:

• WntA knockouts broadly affected wing patterns, altering all scale cell types across tested species.
• Co-mimetic butterfly pairs lacking WntA exhibited significantly different wing patterns.
• Gene networks responsible for wing patterning appear to have diverged considerably between Heliconius lineages.

Conclusions:

• Natural selection can drive phenotypic convergence in wing patterns.
• Divergent developmental contexts between Heliconius lineages provide different developmental routes for achieving resemblance.
• The developmental paths underlying evolutionary convergence can be unpredictable, even with deterministic evolutionary pressures.