The genetic basis and enigmatic origin of melanic polymorphism in pomarine skuas ( <i>Stercorarius pomarinus</i> )
Bibliographic record
Abstract
A key outstanding issue in adaptive evolution is the relationship between the genetics of intraspecific polymorphism and interspecific evolution. Here, we show that the pale/dark ventral plumage polymorphism that occurs in both the pomarine skua ( Stercorarius pomarinus ) and Arctic skua ( S. parasiticus ) is the result of convergent evolution at the same locus ( MC1R ), involving some of the same amino acid sites. The dark melanic MC1R allele in the pomarine skua is strongly divergent from the pale MC1R alleles. Whereas the dark allele is closely related to MC1R alleles in three species of great skua ( S. skua , S. maccormicki , S. lonnbergi ), the pale pomarine skua MC1R alleles present a star-like pattern in an intermediate position on the haplotype network, closer to alleles of the long-tailed skua ( S. longicaudus ). Variation at other nuclear loci confirms a close relationship between the pomarine skua and the great skuas. The plumage polymorphism in pomarine skuas might have arisen in the common ancestor of pomarine and great skuas, only being retained in pomarine skuas. Alternatively, the pale and melanic MC1R alleles may have evolved independently in different lineages and been brought together in pomarine skuas by hybridization. In this case, introgression of a pale MC1R allele into the pomarine skua from another skua lineage is most likely. Our current data do not permit us to distinguish between these hypotheses, and assaying genome-wide variation holds much promise in this regard. Nevertheless, we have uncovered an intriguing example of a functionally important allele within one species that is shared across species.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".