Variation in hypoxia tolerance is driven by evolutionary changes in gene regulation in the eastern oyster

Hypoxia tolerance differs between Louisiana and Texas populations of the eastern oyster (Crassostrea virginica), with genome-wide differentiation showing global FST = 0.21.

• Why it matters: Predicting responses to environmental change requires knowing how stress tolerance evolves, including whether divergence reflects gene regulation or protein-coding evolution.
• What they did: The study combined low-coverage whole-genome sequencing with prior transcriptomic evidence, used FST and diversity metrics to identify candidate regions under recent selection, and tested hypoxia DEGs for elevated divergence.
• The result: Hypoxia DEGs showed higher between-population differentiation, but they were not enriched for nonsynonymous fixed differences (p = 0.9155), supporting regulation changes acting on environmentally responsive pathways.