Genomic evidence for within-species thermal adaptation in collagen genes

Collagen genes in Daphnia magna show within-species thermal adaptation: warmer-climate populations have higher proline and lower serine content in collagen, linked to upper temperature tolerance.

• Why it matters: Variation in collagen composition is known across evolutionary lineages, but its role within a species and its connection to temperature tolerance remained unclear.
• What they did: The study analyzed 39 collagen genes from 215 Daphnia magna populations across three phylogeographic lineages spanning four continents, comparing amino-acid composition with experimentally measured upper temperature tolerance.
• The result: Parallel directional amino-acid shifts occurred across genetically distinct lineages, and collagen genes showed strong positive-selection signatures comparable to immune-related genes, supporting polygenic molecular adaptation to ambient temperature.