Ecological specialization influences OR gene repertoires. Illustrated scatter plot showing the global percentage of pseudogenes within Cetartiodactyla, Carnivora, and Sirenia. The median values of the percentage pseudogenes from high coverage genomic and laboratory generated data for terrestrial, aquatic, and semi-aquatic taxa are depicted along the y-axis. The genomic pseudogenes are considered at 650 bp, which is similar to the length of the PCR product that we amplify. Low-coverage assemblies were excluded.