On the brink: the highly reduced plastomes of nonphotosynthetic Ericaceae
Bibliographic record
Abstract
Ericaceae (the heather family) is a large and diverse group of plants that forms elaborate symbiotic relationships with mycorrhizal fungi, and includes several nonphotosynthetic lineages. Using an extensive sample of fully mycoheterotrophic (MH) species, we explored inter- and intraspecific variation as well as selective constraints acting on the plastomes of these unusual plants. The plastomes of seven MH genera were analysed in a phylogenetic context with two geographically disparate individuals sequenced for Allotropa, Monotropa, and Pityopus. The plastomes of nonphotosynthetic Ericaceae are highly reduced in size (c. 33-41 kbp) and content, having lost all photosynthesis-related genes, and are reduced to encoding housekeeping genes as well as a protease subunit (clpP)-like and acetyl-CoA carboxylase subunit D (accD)-like open reading frames. Despite an increase in the rate of their nucleotide substitutions, the remaining protein-coding genes are typically under purifying selection in full MHs. We also identified ribosomal proteins under relaxed or neutral selection. These plastomes also exhibit striking structural rearrangements. Intraspecific variation within MH Ericaceae ranges from a few differences (Allotropa) to extensive population divergences (Monotropa, Hypopitys), which indicates that cryptic speciation may be occurring in several lineages. The pattern of gene loss within fully MH Ericaceae plastomes suggests an advanced state of degradation.
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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".