Fig. 5.

Discovery of monogamy candidate genes (OGGs). To ensure a rigorous and conservative approach toward identifying OGGs robustly associated with monogamy across clades, any given gene/OGG had to fulfill two selection criteria. First, an OGG had to show a ±1 log₂ fold expression difference between the monogamous and nonmonogamous species in at least four clades. Second, an OGG had to be among the most up- or the most down-regulated in 6 of the 10 RRHO analyses (as shown in Fig. 4); this again required an OGG to be concordantly expressed in at least four of the five lineages. Which clade (if any) is nonconcordant can vary for each OGG. Relative expression levels of these candidates are illustrated in the heatmap. Note that no clade is more often discordant than any other (SI Appendix, Table S7).