Genomic signatures of positive selection and relaxed selective constraints associated with convergent dietary specialisation

Positive selection signatures in protein-coding genes in two island specialist Dysdera lineages are linked to a twofold increase in gene loss rates versus generalist ancestors.

• Why it matters: Island radiations offer a way to test how convergent dietary shifts reshape genomes, including whether adaptation and constraint relaxation follow predictable patterns.
• What they did: Using six high-quality genome assemblies from two independent dietary-specialisation events, the study scanned protein-coding genes, upstream regulatory regions, and gene family turnover rates for positive selection and relaxed constraints.
• The result: Selection acted on a smaller, functionally coherent gene set, potentially tied to detoxification via heavy metal excretion, while relaxed selection involved broader, potentially dispensable functions and gene family contractions in vesicular transport.

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