18S rDNA sequence-structure phylogeny of the Chlorophyceae with special emphasis on the Sphaeropleales

Using THESES db, the algae 18S rDNA sequence-structure database for inferring phylogenies, we reconstructed the phylogeny of a comprehensive sampling of sphaeroplealean green algae evaluated in the context of chlorophycean diversity. A review of the most recent assessments of chlorophycean phylogeny using sequence-only analyses further illustrates the contrast with results obtained from chlorophycean 18S rDNA sequence-structure analysis to the current literature on chlorophycean phylogenomics. With only the phylogenetic position of Golenkinia and the Cylindrocapsa-clade as exceptions, a maximum likelihood tree of 18S rDNA sequence-structure data is robustly supported and is almost fully congruent with the tree topology obtained by the most recent phylogenomic approaches. Remarkably, even a quick and easy neighbor-joining analysis yields accurate results and enables one to reconstruct and discuss the big picture for all three hundred sphaeroplealean 18S rDNA sequence-structure pairs currently available. These results are testament to the ease, utility and power of a sequence-structure approach to analyzing 18S rDNA data.