SSU rDNA phylogeny. Gamma-corrected maximum likelihood tree (-lnL = 8391.020304, α = 0.378, 4 rate categories) inferred using the GTR model of substitution on an alignment of 45 SSU rDNA sequences and 1693 unambiguously aligned sites. Numbers at the branches denote bootstrap percentages using maximum likelihood – GTR (top) and Bayesian posterior probabilities – GTR (bottom). Black dots on branches denote bootstrap percentages and posterior probabilities of 95% or higher. Accession numbers represent environmental sequences of unknown identity. Sequences derived from this study are highlighted in black boxes and the image/s in Fig 1 representing the taxon are cited. I = morphotype I of the genus Warnowia; c = containing chloroplasts; n = possessing nematocysts.