Studies on the pollen-trapping fungal genus Retiarius: Taxonomy, phylogenetics, and metabolism with a special focus on western Canada
Bibliographic record
Abstract
Fungi can obtain nutrients from a variety of sources, including some which capture and degrade pollen grains. Retiarius Olivier (Orbiliomycetes, Ascomycota) is an anamorphic hyphomycete that traps airborne pollen grains with aerial hyphae. Only four species, described from South Africa and Hungary, are known within the genus. Retiarius has been widely reported in Europe, with several dispersed records world-wide including a single record from North America. In recent years, Retiarius has been detected in metagenome sequencing projects of lichens. In addition, microscopic observations of pollen grain deposits on the undersurfaces of lichens revealed hyphae infecting pollen grains. With these observations, I suspected that Retiarius was more prevalent in Western Canada than the previous sampling would suggest. In my thesis, I developed genus-specific PCR primers to screen for the presence of Retiarius on lichens and adjacent substrate from forests in Canada, the western US, and northern Mexico. I isolated strains in axenic culture of Retiarius from the lower surface of rock-dwelling lichens. Two of the strains were used in phenotype profiling experiments to characterize carbon and nitrogen utilization. The environmental screening suggested that Retiarius is ubiquitous in lichens and adjacent substrates of all forested ecosystems included in my sampling. In the Canadian Arctic, Retiarius was detected at low frequency rates. Phylogenetic analyses using a multilocus tree revealed two undescribed species: Retiarius canadensis nom. prov., and Retiarius crescentus nom. prov. Both were isolated from the lower surface of lichens, with morphological characteristics different from the known species of Retiarius. Using sequences derived from environmental sequencing, I identified an additional 17 putative species-level lineages of Retiarius. The phenotype profiling data were inconsistent in characterizing Retiarius carbon and nitrogen utilization. As a resource for future studies, the genome of Retiarius crescentus nom. prov. was sequenced and annotated, representing the first genome of a non-nematode trapping species in Orbiliomycetes. This research will serve as a benchmark for studying the genus Retiarius, expanding the current knowledge of its phylogeny and species richness. The evidence indicates a great diversity of species yet to be described, present in a wide variety of ecosystems across North America, and it might play a key role in nutrient cycling by tapping into the nutrient-rich pollen grains.
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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 | 0.003 | 0.005 |
| Science and technology studies | 0.003 | 0.000 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".