Evaluating the presence and introgression of the hybrid forest pathogen Cronartium x flexili
Bibliographic record
Abstract
The recent discovery of a hybrid forest fungal pathogen, Cronartium x flexili, suggested to have arisen from sexual hybridization between the introduced C. ribicola and the native C. comandrae, was surprising because the parental species do not share hosts. Although the pathosystems of both parental species are well described, the impact of their hybridization is yet unknown. The purpose of this study is to determine the occurrence, level of hybridization and introgression of the hybrid pine stem rust Cronartium x flexili. A total of 831 samples from dikaryotic aecia of C. ribicola and C. comandrae were collected from 13 sites across British Columbia and Alberta and analysed both genetically and morphologically over two sampling seasons. Microscopic and genetic methods, including PCR, qPCR, and genotyping by sequencing (GBS), were used to identify hybrid samples. The results of these analyses indicate that C. x flexili is either no longer prevalent in areas where it was previously found, or else prevalent at such low frequencies that it has evaded detection in the sampling effort of this study. Two previously collected and extracted C. x flexili DNA samples were examined using a fixed loci analysis and did not demonstrate evidence of introgression, indicating that this hybrid does not facilitate gene flow between the introduced C. ribicola and the native C. comandrae. This suggests that when a hybridization event occurs between the parental Cronartium spp., first generation (F1) hybrids result but are not fertile and do not occur perennially. Some evidence suggests that this could be due to a number of factors including: low relative fitness of C. x flexili compared to the parental species if ‘hybrid breakdown’ occurs as explained by the Bateson-Dobzhansky-Muller incompatibility (BDMI) model; variations in local climate factors influencing life cycle parameters; or sexual incompatibility with the parental species. This work adds to the limited literature on the genetics of hybrid forest fungal pathogens and improves our understanding of the evolutionary mechanisms occurring when allopatrically evolved forest fungal species hybridize.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 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".