Origin, Evolution, and Extinction of Asexual Fungi: Experimental Tests Using<i>Cryptococcus neoformans</i>
Bibliographic record
Abstract
This chapter reviews and discusses recent experimental studies using the model basidiomycetous yeast Cryptococcus neoformans to test the effects of spontaneous mutations and biological interactions that may have contributed to the distribution of asexual fungal strains and species in nature. To begin with, the author first introduces some background information on fungal sexuality and spontaneous mutations. The study of fungal sexuality could be traced back to over 100 years ago when Blakeslee discovered obligatory cross-fertilization in the Mucorales. At the population level, evidence for clonality and asexual reproduction has been found in many groups of microorganisms, including both sexual and asexual fungi. Spontaneous mutation is the ultimate source of all heritable variations in all organisms. It can occur in both replicating and nonreplicating genetic materials in cells or viral particles. The genome-wide mutation rate and the average effect per mutation are most commonly estimated using mutation accumulation (MA) experiments. In these experiments, spontaneous mutations are allowed to accumulate in replicate lines in the absence of selection for the trait under investigation. Sexuality in fungi is typically considered a qualitative trait. Two strains are considered either capable or not capable of mating with each other to produce meiotic progeny. The chapter summarizes three recent studies that tested the three hypotheses on fungal asexuality: the loss of sex, the cost of sex, and the fitness consequences of fungal asexual clones in experimental populations of C. neoformans
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| 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".