Sexing carnivores from faecal metagenomes: calibrating Rx for stone marten and red fox

The X-to-autosome ratio sexing metric Rx, calibrated for stone marten (Martes foina) and red fox (Vulpes vulpes), misassigned only 9 of 11,200 subsamples.

• Why it matters: Scat-based metagenomic monitoring gains value from knowing depositor sex, but human ancient-DNA read-ratio methods did not work reliably in carnivore shotgun metagenomes.
• What they did: After removing human DNA by competitive mapping, the authors tested Skoglund Ry on seven marten and fox scats, then reimplemented Rx and simulated male/female genomes with 200 replicates across 14 depths from 1,000 to 100,000 mapped reads.
• The result: Rx’s human-derived thresholds misassigned only below 2,000 mapped reads, while failures above 7,500 reads were non-assignments in under 5% of replicates and under 1% above 15,000; applied to scats, it sexed four females and two males, leaving one sample unassigned.

AI summary of the abstract · may contain errors · not medical advice · read the paper.