Maximum-likelihood (ML) trees built from the alignments of V4 18S rDNA sequences. Molecular phylogeny of (a) isolated diatom groups and (b) Chlorophyceae with related clades. Nucleotide sequences obtained in the underlying study indicated by species names in bold. Further sequences were obtained from the SILVA database (http://www.arb-silva.de) given with accession numbers. The trees with the highest log likelihood ((a) -1355.5135; (b) -2321.7603) were inferred using the Maximum Likelihood method based on the Kimura 2-parameter model with MEGA6. The fraction of replicate trees in which the associated taxa clustered together is shown next to the branches (1000 bootstraps). The outgroups were (a) Arabidopsis thaliana and (b) Mus musculus. All positions with less than 80% site coverage were excluded for tree construction. The scale bar represents number of substitutions per site.