Comparative Genomics Reveals Adaptive Protein Evolution and a Possible Cytonuclear Incompatibility between European and American Eels
Bibliographic record
Abstract
During the early stages of speciation, interspecific gene flow may be impeded by deleterious epistatic interactions in hybrids, which maintain parental allelic combinations at the speciation genes. The resulting semipermeable nature of the barrier to interspecific gene flow provides a valuable framework to identify the genes involved in hybrid mortality or sterility, as well as the evolutionary mechanisms that initially caused their divergence. The two Atlantic eels Anguilla anguilla and A. rostrata are partially isolated sister species that naturally hybridize, but whose genetic basis of postzygotic isolation remains unknown. We collected high-throughput sequencing data from the transcriptomes of 58 individuals and discovered 94 genes showing differentially fixed mutations between species. Evidence for positive selection at nuclear diagnostic genes was obtained using multilocus extensions of the McDonald-Kreitman test with polymorphism data from each species. In contrast, mitochondrial protein-coding genes experienced strong purifying selection and mostly diverged at synonymous sites, except for the mt-atp6 gene, which showed an atypically high nonsynonymous to synonymous rate ratio. Nuclear-encoded protein interactors of the mt-atp6 gene in the ATP synthase complex were significantly overrepresented in the list of nuclear diagnostic genes. Further analysis of resequencing data showed that positive selection has operated at both the mt-atp6 gene and its nuclear interactor atp5c1. These findings suggest that a cytonuclear incompatibility caused by a disruption of normal ATP synthase function in hybrids contributes to partial reproductive isolation between European and American eels.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".