Evidence for extensive diversity in the pollen-parasitic genus <i>Retiarius</i> in western North America, including two new species associated with lichens
Bibliographic record
Abstract
Understanding the diversity of microscopic hyphomycetes is an ongoing effort, and many species remain undescribed. While studying lichen organismal composition in western Canada, metagenomic data revealed the presence of an unknown species of Retiarius (Orbiliaceae, Ascomycota), a genus of pollen-parasitic fungus with no previous records in the region. We developed genus-specific primers to amplify Retiarius DNA in lichen and adjacent substrate extractions, successfully detecting multiple lineages of Retiarius across a wide geographic range within North America. We proceeded to screen accumulations of pollen on the undersurface of lichen thalli to isolate any pollen-associated fungi. Using dilution series and PCR for identification, we isolated two specifically distinct strains of Retiarius with morphology unlike any described member of the genus. Inclusion of DNA from these strains in a multilocus phylogeny using the internal transcribed spacer regions ITS1-5.8S-ITS2 (ITS), partial nuc 28S rDNA (28S), and nuc small subunit (18S) confirmed their evolutionarily distinct position in the genus. We describe these two species here as Retiarius canadensis and R. crescentus. The former possesses trinacrium-shaped conidia, similar to those of R. bovicornutus and R. revayae but morphometrically different, and the latter is distinguished by its canoe-shaped conidia, a morphological character heretofore unknown from Retiarius.
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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 | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".