Ecotype partitioning by olfactory receptor genes. (A) Heatmap of the informative OR gene families partitioned by ecological group (color bars on right follow legend). (B) Naïve Bayes pattern analysis of OR gene repertoires showing species assignment into ecological groups: (pink) volant, (red) terrestrial, (blue) aquatic, or (green) semi-aquatic based on the familial distribution of OR genes. Species abbreviations follow A (color bars on top follow legend). (C) Scatterplots showing the results of PCA analysis on functional OR genes within their respective OR gene families. The first and second axes explain 70% of the variance within the data set (ANOSIM: r = 0.6095, P < 0.001). Colored polygons highlight the different ecological groups of mammals. (Green lines) The contribution of particular families to the first two principal components. Species abbreviations, including ancestors, follow A. (D) Close-up view of the terrestrial polygon in C (boxed).