Phylogeography of white spruce (<i>Picea glauca</i>) in eastern North America reveals contrasting ecological trajectories
Bibliographic record
Abstract
Abstract Aim The main objective of this study was to investigate the origin of white spruce (Picea glauca) range discontinuities in eastern North America. A first analysis aimed at uncovering the glacial origin and post‐glacial migration route of white spruce in the eastern part of the range. A second analysis aimed at evaluating whether disjunct white spruce populations in central Québec result from a recent expansion or are remnant stands following a northern range contraction. Location The first analysis covered the North American transcontinental boreal distribution of white spruce, and the second focused on the eastern part of its range. Methods A total of 589 P. glauca individuals from 51 populations, 24 of which were from a previous published source, were analysed for variation in three chloroplast DNA regions (trnT/L, trnL/F and ndhK/C). At the continental scale, haplotypic diversity, zones of genetic discontinuities, clustering analysis and analysis of molecular variance (AMOVA) were employed. In the eastern part of the range, haplotypic diversity was assessed with a permutation procedure, demographic history with mismatch analyses, and genetic structure with AMOVA. Results At the continental scale, various lines of evidence (genetic‐diversity hotspots, endemic haplotypes, zones of genetic discontinuities, and pattern of molecular variation) show that different lineages migrated from three glacial refugia (Beringian, Mississippian, east Appalachian). Strong genetic discontinuities, low diversity and lack of evidence for demographic expansion were found among stands from isolated high hills in central Québec. Main conclusions White spruce in the eastern part of its range has an east Appalachian origin, a lineage genetically distinct from populations west of the Great Lakes. Previous studies have shown that the northward migration of white spruce is still ongoing as the northernmost populations expand into the tundra. In contrast, mixed white spruce and balsam fir (Abies balsamea) stands from isolated high hills in central Québec have already reached their Holocene maxima and are currently declining. This range contraction is probably a result of increased wildfire disturbance, which gradually creates a pattern of regional white spruce isolation and replacement by fire‐prone black spruce (Picea mariana) forest.
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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".