The taxonomic distribution of C<sub>4</sub> photosynthesis in Amaranthaceae sensu stricto
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Bibliographic record
Abstract
C(4) photosynthesis evolved multiple times in the Amaranthaceae s.s., but the C(4) evolutionary lineages are unclear because the photosynthetic pathway is unknown for most species of the family. To clarify the distribution of C(4) photosynthesis in the Amaranthaceae, we determined carbon isotope ratios of 607 species and mapped these onto a phylogeny determined from matK/trnK sequences. Approximately 28% of the Amaranthaceae species use the C(4) pathway. C(4) species occur in 10 genera-Aerva, Amaranthus, Blutaparon, Alternanthera, Froelichia, Lithophila, Guilleminea, Gomphrena, Gossypianthus, and Tidestromia. Aerva, Alternanthera, and Gomphrena contain both C(3) and C(4) species. In Aerva, 25% of the sampled species are C(4). In Alternanthera, 19.5% are C(4), while 89% of the Gomphrena species are C(4). Integration of isotope and matK/trnK data indicated C(4) photosynthesis evolved five times in the Amaranthaceae, specifically in Aerva, Alternanthera, Amaranthus, Tidestromia, and a lineage containing Froelichia, Blutaparon, Guilleminea, Gomphrena pro parte, and Lithophila. Aerva and Gomphrena are both polyphyletic with C(3) and C(4) species belonging to distinct clades. Alternanthera appears to be monophyletic with C(4) photosynthesis originating in a terminal sublineage of procumbent herbs. Alpine C(4) species were also identified in Alternanthera, Amaranthus, and Gomphrena, including one species (Gomphrena meyeniana) from 4600 m a.s.l.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.000 | 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 it