The balanced lethal system in <i>Triturus</i> newts originated in an instantaneous speciation event.
Bibliographic record
Abstract
The balanced lethal system found in crested and marbled newts of the genus Triturus presents an intriguing mystery. All adults possess two distinct forms of their largest chromosome, resulting in 50% of offspring inheriting two copies of one of these forms. These homomorphic individuals undergo fatal developmental arrest during embryogenesis. How could such an obviously maladaptive trait, destroying half of an organism's reproductive output, evolve? We construct a high-density linkage maps for Triturus and its sister genus Lissotriton , identifying genes involved in the balanced lethal system. We find that each of the two forms of Triturus chromosome 1 is characterized by a single massive deletion. Ploidy analysis shows that each deletion is compensated for by a duplication of the same region on the opposite chromosome. This suggests that the balanced lethal system was created suddenly, as the result of an unequal exchange between chromosomes in a single individual. We simulate the consequences of such a mutation, finding that, if the rearranged chromosomes exert a fitness penalty when combined with the ancestral version, a stable balanced lethal system can become fixed within a population. Counterintuitively, the deleterious nature of the rearranged chromosomes causes reproductive isolation that protects them from invasion by their fitter ancestor. We conclude that the origin of the Triturus balanced lethal system is effectively an instantaneous speciation event, which resulted in the fixation of the balanced lethal system.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".