Phylogenetic relationships among selected genomes in the Prochlorococcus marinus/marine Synechococcus group. Each point in a triangle (simplex) represents a set of orthologous genes that contains at least four analyzed genomes (and as many as 19 genomes from this group). Position of the point in the barycentric coordinate system (triangle) depends on bootstrap support values for each of three possible tree topologies with which each vertex is associated. The closer the point to the vertex, the higher its bootstrap support for that tree topology. Poorly resolved relationships result in points located closer to the center of the triangle. Values at each vertex refer to the number of sets of orthologous genes that support the tree topology at the vertex overall, with at least 80% and at least 90% bootstrap support, respectively. For a full description of the methodology used to analyze embedded quartets, see Zhaxybayeva and Gogarten (2003) and Zhaxybayeva et al. (2006). Genomes are designated by their strain names. (Bold) Genomes of marine Synechococcus spp., (italics) low-light adapted Prochlorococcus marinus genomes, (plain font) Prochlorococcus marinus high-light adapted strains (all genomes are from NCBI's RefSeq database). Full analyses of the phylogenetic relationships within this group as well as details on the selection of sets of orthologous genes and phylogenetic analyses performed will be presented elsewhere (O. Zhaxybayeva, F. Doolittle, T. Papke, and P. Gogarten, in prep.).
