Figure 4From: Molecular subdivision of the marine diatom Thalassiosira rotulain relation to geographic distribution, genome size, and physiologyPhylogenetic Analysis. Bayesian analysis of divergence times among Thalassiosira spp. based on rDNA ITS1 sequence alignment. Time estimates are derived from a relaxed molecular clock calibrated using Sorhannus [12]. Branch numbers represent time of divergence (Mya). Chronogram shows that T. rotula split from T. gravida approximately 3.28 Mya. Within T. rotula, Lineages 1 and 2 split from Lineage 3 approximately 0.68 Mya. Lineages 1 and 2 diverged from one another approximately 0.22 Mya. The tree topology matches that of Sorhannus [12], with the divergence of T. pseudonana from all other Thalassiosira spp at 30 Mya. Placement of T. weissflogii and T. guillardii differ from Sorhannus [12], which may be due to differences in ITS1 and 18S mutation rates.Back to article page