FIGURE 9.

Proposed evolutionary model for the Ecdysozoans and Lophotrochozoan family B1 GPCRs. The main metazoan receptor subfamily gene clusters are represented by full colored circles according to their proposed common origin in the bilaterian ancestral genome. Four genes precursors for family B GPCR subfamilies arouse from gene duplication events in the bilaterian ancestral genome. These genes subsequently evolved under distinct evolutionary pressures in the protostome and deuterostome lineages (for more details see Cardoso et al., 2014). Species-specific gene duplications/deletions within each receptor family are not represented. The two rounds of genome duplication (1R and 2R) in the deuterostome radiation are represented. The phylogeny of Cluster B is represented in Supplementary Figure 1. The rest of the data was obtained from Cardoso et al. (2006; 2010, unpublished; On et al., 2015). The figure was adapted from Cardoso et al. (2014) and is not drawn to scale.