Fig. 4
From: Convergent degeneration of olfactory receptor gene repertoires in marine mammals
Comparative analysis of OR gene selective pressure. a Boxplots of the comparison between Class I (blue) and Class II (pink) OGGs for estimated ω values. b Boxplots of the comparison between the estimated ω values of OGGs containing marine mammals and excluding terrestrial mammals (Mann-Whitney U test used to test the difference). c Number of intact genes in each OGG is positively correlated with the estimated ω value of the respective OGG, and the dashed line indicates the regression line. d Estimated ω value for an OGG was positively correlated with the gene amplification number in the respective OGG. e Estimated ω value for an OGG was positively correlated with gene loss number in the respective OGG. The correlation coefficients (r) of (c), (d) and (e) are 0.129, 0.221 and 0.253, and the p values are 1.24 × 10− 3, 2.51 × 10− 8 and 1.56 × 10− 10, respectively