Evaluating genomic divergence and parallelism in replicate ecomorphs from young and old cichlid adaptive radiations

Area of Science:

• Evolutionary biology
• Genomics
• Speciation research

Background:

• Comparative genomic studies often examine single species pairs, limiting understanding of the speciation continuum.
• Investigating multiple species pairs at different divergence times is crucial for understanding evolutionary processes.

Purpose of the Study:

• To examine genomic divergence patterns across three sympatric cichlid species pairs with varying ages but similar ecological differentiation.
• To infer the continuum of evolutionary divergence during speciation.

Main Methods:

• Whole-genome resequencing of three sympatric cichlid species pairs.
• Analysis of genomic patterns of divergence in mitochondrial and nuclear genomes.
• Comparison of outlier regions to detect signatures of convergent evolution.

Main Results:

• Genomic divergence, both absolute and relative, increases significantly with evolutionary time in cichlids.
• Regions of elevated differentiation showed increased absolute differentiation, contrasting with other systems.
• A modest signature of convergent evolution was detected in outlier regions across species pairs.

Conclusions:

• Strong functional and phenotypic differentiation in cichlids is associated with clear genomic divergence, even in young species pairs.
• Evolutionary divergence in cichlids appears repeatable but polygenic.
• The study provides insights into the genomic underpinnings of speciation and adaptation.