Population Divergence in the Eastern North American Boreal Forests: Extensive Gene Flow Characterises a Hybrid Zone Between Palm Warbler Subspecies (Parulidae: <i>Setophaga palmarum</i>)
Bibliographic record
Abstract
Pleistocene glaciations have shaped much of the population divergence events in the coniferous forests of North America. However, unlike in western North America, the evidence for forest fragmentation and population divergence associated with glacial cycles is less clear in the boreal forests of eastern North America. Here, we present the first genomic analysis of an avian hybrid zone in the eastern North American boreal forest between two subspecies of Palm Warblers (Setophaga palmarum). Using both genomic and plumage datasets, we characterise the divergence history of the two subspecies and relate our findings to the larger biogeographic history of the region. We find the Palm Warbler subspecies to have diverged in the mid-Pleistocene (~831 KYA) and have experienced near-continuous gene flow since initial splitting, resulting in a wide hybrid zone and little evidence of reproductive isolation. Coalescent modelling further indicates that the divergence of these two subspecies is congruent with the effects of glacial cycles and suggests a shared biogeographic history with the sole other known example of avian divergence in the region. However, in addition to the general paucity of such events, both of the known divergence events in the eastern boreal forests are characterised by low differentiation at present. This suggests that the conditions in the proposed eastern glacial refugia may not have been sufficient in establishing strong reproductive isolation, which perhaps explains why speciation events have been relatively rare in the eastern boreal forests of North America.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| 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".