Pleistocene glacial cycles and physical barriers influence phylogeographic structure in Black-capped Chickadees (<i>Poecile</i> <i>atricapillus</i>), a widespread North American passerine
Bibliographic record
Abstract
The nonmigratory Black-capped Chickadee (Poecile atricapillus (Linnaeus, 1766)) has a continent-wide distribution extending across large parts of North America. To investigate the phylogeographic structure and verify possible refugia during the last glacial maximum, we sequenced a 678 bp region of the mitochondrial control region from 633 Black-capped Chickadees at 35 sites across North America and performed paleoecological distribution modeling. Two genetically distinct groups were found using multiple analyses: one in Newfoundland (Canada) and a widespread continental group, with additional substructure evident in western continental populations. While gene flow is low throughout the range, it is especially low in peripheral populations. The Newfoundland population has remained isolated from continental populations for at least 65 000 years and contains a number of fixed nucleotide differences. Within the continental populations, Black-capped Chickadees are subdivided into Pacific Coast, Alaska (USA), southeast Rockies, and main-northeast groups consistent with late Pleistocene vicariance events. Evidence of secondary contact was identified between Pacific and main-northeast populations in northwest British Columbia (Canada) and between southeast Rockies and main-northeast groups in Montana (USA). Paleoecological distribution modeling predicted suitable habitat in Alaska, off the coast of Newfoundland, and several locations across the southern United States during the last glacial maximum, whereas suitable habitat during the last interglacial was more similar to the contemporary distribution.
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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 | 0.001 |
| 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 | 0.001 | 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".