Rescued from extinction in two buckets: genomic consequences of an extreme bottleneck in the endangered Owens pupfish

The Owens pupfish (Cyprinodon radiosus) shows low genome-wide genetic diversity and a 17-fold contraction in effective population size after a severe bottleneck estimated at 400 individuals.

• Why it matters: Bottlenecks can reduce genetic diversity and effective population size while increasing inbreeding, threatening viability—especially in freshwater fishes facing fragmentation and habitat loss.
• What they did: Whole-genome sequencing of 12 individuals from two Owens pupfish populations (one extirpated, one extant) reconstructed recent demographic history and quantified diversity, effective population size, and inbreeding.
• The result: The bottleneck timing was estimated precisely to 1977–1985, and low inbreeding likely predated it; results suggest reduced diversity and low effective size may constrain adaptive potential.