A unique mode of parasitism in the conifer coral tree<i>Parasitaxus ustus</i>(Podocarpaceae)
Bibliographic record
Abstract
ABSTRACT Almost all parasitic plants, including more than 3000 species, are angiosperms. The only suggested gymnosperm exception is the New Caledonian conifer,Parasitaxus ustus, which forms a bizarre graft‐like attachment to the roots of another coniferFalcatifolium taxoides. Yet, the degree of resource dependence ofParasitaxusonFalcatifoliumhas remained speculative. Here we show thatParasitaxusis definitively parasitic, but it displays a physiological habit unlike any known angiosperm parasite. Despite possessing chloroplasts, it was found that the burgundy red shoots ofParasitaxuslack significant photosynthetic electron transport. However unlike non‐photosynthetic angiosperm parasites (holoparasites), tissues ofParasitaxusare considerably enriched in13carbon relative to its host. In line with anatomical observations of fungal hyphae embedded in the parasite/host union, stable carbon isotopic measurements indicate that carbon transport from the host toParasitaxusmost likely involves a fungal partner. Therefore,Parasitaxusparallels fungus‐feeding angiosperms (mycoheterotrophs) that steal carbon from soil mycorrhizal fungi. Yet with its tree‐like habit, association with fungi residing within the host union, high stomatal conductance, and low water potential, it is demonstrated thatParasitaxusfunctions unlike any known angiosperm mycoheterotroph or holoparasite.Parasitaxusappears to present a unique physiological chimera of mistletoe‐like water relations and fungal‐mediated carbon trafficking from the host.
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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 | 0.000 | 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) | 0.001 | 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".