Joint inferences from cytoplasmic <scp>DNA</scp> and fossil data provide evidence for glacial vicariance and contrasted post‐glacial dynamics in tamarack, a transcontinental conifer
Bibliographic record
Abstract
Abstract Aim Tamarack (Larix laricina) is an early‐successional transcontinental boreal conifer occurring within the spruce‐fir dominated forest. The aim was to infer the species biogeographical history and to assess the putative genetic imprint left by interspecific competition during post‐glacial migration, using cytoplasmic DNA and fossil data. Location Forty‐five locations were sampled across the transcontinental range spanning the North American boreal forest. Methods A total of 621 trees were scanned for mitochondrial and chloroplast DNA polymorphisms to reveal geographical patterns of genetic diversity, differentiation, and population structure throughout the species range. Published pollen records were analysed to assess the chronology of post‐glacial colonization of Larix sp. relative to more competitive tree taxa, Picea sp. and Abies sp.. Results Genotyping resulted in two mitotypes (one locus) and 24 chlorotypes (three cpSSR loci). Bayesian assignment test based on cpDNA data detected three groups: eastern North America, western North America and Alaska. CpDNA population differentiation was higher in the western part of the range relative to the eastern part. Post‐glacial colonization chronology derived from fossil data indicated that Larix colonized western North America at least 4000 years after Picea and Abies, but shortly preceded them in eastern North America. Main conclusions Cytoplasmic and fossil data provided support for four distinct glacial lineages. Two lineages would have persisted south of the Laurentide ice sheet, while the two remaining ones likely originate from northern refugia located in Beringia and Labrador. Larix establishment was possibly hindered by earlier establishment of more competitive taxa in western North America, which resulted in high genetic differentiation among western populations. These results provide support for a putative role of interspecific competition in structuring the standing genetic variation at the time of post‐glacial colonization.
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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 | 0.001 |
| Science and technology studies | 0.001 | 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".