Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.
Bibliographic record
Abstract
The green plants (Viridiplantae) are an ancient group of eukaryotes comprising two main clades: the Chlorophyta, which includes a wide diversity of green algae, and the Streptophyta, which consists of freshwater green algae and the land plants. The early-diverging lineages of the Viridiplantae comprise unicellular algae, and multicellularity has evolved independently in the two clades. Recent molecular data have revealed an unrecognized early-diverging lineage of green plants, the Palmophyllales, with a unique form of multicellularity, and typically found in deep water. The phylogenetic position of this enigmatic group, however, remained uncertain. Here we elucidate the evolutionary affinity of the Palmophyllales using chloroplast genomic, and nuclear rDNA data. Phylogenetic analyses firmly place the palmophyllalean Verdigellas peltata along with species of Prasinococcales (prasinophyte clade VI) in the deepest-branching clade of the Chlorophyta. The small, compact and intronless chloroplast genome (cpDNA) of V. peltata shows striking similarities in gene content and organization with the cpDNAs of Prasinococcales and the streptophyte Mesostigma viride, indicating that cpDNA architecture has been extremely well conserved in these deep-branching lineages of green plants. The phylogenetic distinctness of the Palmophyllales-Prasinococcales clade, characterized by unique ultrastructural features, warrants recognition of a new class of green plants, Palmophyllophyceae class. nov.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".