Redefining<i>Humicola sensu stricto</i>and related genera in the<i>Chaetomiaceae</i>
Bibliographic record
Abstract
The traditional concept of the genusHumicolaincludes species that produce pigmented, thick-walled and single-celled spores laterally or terminally on hyphae or minimally differentiated conidiophores. More than 50 species have been described in the genus. Species commonly occur in soil, indoor environments, and compost habitats. The taxonomy ofHumicolaand morphologically similar genera is poorly understood in modern terms. Based on a four-locus phylogeny, the morphological concept ofHumicolaproved to be polyphyletic. The type ofHumicola,H. fuscoatra, belongs to theChaetomiaceae. In theChaetomiaceae, species producing humicola-like thick-walled spores are distributed among four lineages:Humicola sensu stricto,Mycothermus,Staphylotrichum,andTrichocladium. In our revised concept ofHumicola, asexual and sexually reproducing species both occur. The re-definedHumicolacontains 24 species (seven new and thirteen new combinations), which are described and illustrated in this study. The species in this genus produce conidia that are lateral, intercalary or terminal on/in hyphae, and conidiophores are not formed or are minimally developed (micronematous). The ascospores of sexualHumicolaspecies are limoniform to quadrangular in face view and bilaterally flattened with one apical germ pore. Seven species are accepted inStaphylotrichum(four new species, one new combination). Thick-walled conidia ofStaphylotrichumspecies usually arise either from hyphae (micronematous) or from apically branched, seta-like conidiophores (macronematous). The sexual morph represented byStaphylotrichum longicolleum(=Chaetomium longicolleum) produces ascomata with long necks composed of a fused basal part of the terminal hairs, and ascospores that are broad limoniform to nearly globose, bilaterally flattened, with an apical germ pore. TheTrichocladiumlineage has a high morphological diversity in both asexual and sexual structures. Phylogenetic analysis revealed four subclades in this lineage. However, these subclades are genetically closely related, and no distinctive phenotypic characters are linked to any of them. Fourteen species are accepted inTrichocladium,including one new species, twelve new combinations. The type species ofGilmaniella,G. humicola, belongs to the polyphyletic familyLasiosphaeriaceae(Sordariales), butG. macrosporaphylogenetically belongs toTrichocladium. The thermophilic genusMycothermusand the type speciesMy. thermophilumare validated, and one newMycothermusspecies is described. Phylogenetic analyses show thatRemersonia, another thermophilic genus, is sister toMycothermusand two species are known, including one new species.Thermomyces verrucosusproduces humicola-like conidia and is transferred toBotryotrichumbased on phylogenetic affinities. This study is a first attempt to establish an inclusive modern classification ofHumicolaand humicola-like genera of theChaetomiaceae. More research is needed to determine the phylogenetic relationships of “humicola”-like species outside theChaetomiaceae.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".