One gene, multiple alleles: insights into the microevolution of pigmentation polymorphisms

Area of Science:

• Evolutionary biology
• Developmental genetics
• Population genetics

Background:

• Understanding the genetic and developmental basis of phenotypic variation is crucial for evolutionary biology.
• Discrete polymorphisms in wild populations, particularly concerning morphological diversity, remain poorly understood.
• Integrating studies of developmental mechanisms with population genetics is challenging but essential for evolutionary insights.

Discussion:

• Roberts et al. investigate a polymorphic blotched coloration in Lake Malawi cichlids, linking it to a noncoding single nucleotide polymorphism (SNP) upstream of the pax7a gene.
• Phenotypic differences arise from alterations in pigment cell development and survival, detailed through developmental analysis.
• Controlled crosses and population genetics identified three pax7a dominant blotch alleles associated with specific morphs, leading to varied pax7a transcript levels and pigment cell composition.

Key Insights:

• The study bridges the gap between evolutionary developmental genetics and population genetics.
• Identified pax7a alleles explain the diverse pigmentation patterns observed in cichlid females.
• A common origin for the blotched morph allele was found, followed by sequential evolution of derived alleles contributing to morph diversity.

Outlook:

• This research provides a mechanistic understanding of morphological innovation and diversification.
• Further investigation into the evolutionary history of the pax7a allelic series can illuminate speciation processes.
• The findings pave the way for studying similar genetic underpinnings of phenotypic variation in other species.