FIGURE 8.1 Molecular phylogenies based on COI (COI plus ATPase8/6 for Diadema) from eight sea urchin genera. Data are from Lessios et al. (1999, 2003a,b), Zigler and Lessios (2004), McCartney et al. (2000), Landry et al. (2003), Biermann et al. (2003), Metz et al. (1998), Zigler et al. (2003). The double arrows mark the completion of the Isthmus of Panama at ≈3.1 million years ago. This date is assumed to be approximate for the divergence of Caribbean and eastern Pacific species within the six genera marked by the arrows. Trees are rooted by species from closely related genera [see Biermann et al. (2003), Landry et al. (2003), Lessios et al. (1999, 2003a,b), McCartney et al. (2000), Metz et al. (1998), Zigler and Lessios (2004), Zigler et al. (2003) for details] and are drawn to the same temporal scale. See the text for group definitions.