Phylogeography, introgression, and population structure of the eastern North American birches Betula alleghaniensis, B. papyrifera, and B. lenta
Bibliographic record
Abstract
This study examines phylogeography, population genetics, and introgression in birches (Betula spp.) of eastern North America with a specific focus on B. papyrifera Marsh., B. alleghaniensis Britt., and B. lenta L. Betula papyrifera (2n=56, 70, 84)occupies a wide variety of habitats across the transcontinental boreal zone and into northeastern temperate forests. Betula alleghaniensis (2n=84) is a mesophytic species occurring from southeastern Canada and New England to the southern Appalachians. Betula lenta (2n=28) is endemic to the Appalachian region of the United States, where it occurs primarily on moist, cool sites. Phylogeographic analyses based on chloroplast DNA (cpDNA) markers were used for inferring locations of glacial refugia and patterns of post-glacial migration. Nuclear microsatellite markers were used for investigating \nallelic richness, gene diversity, and genetic structure of populations of each species. The haplotype sharing among species was examined to elucidate patterns of cpDNA \nintrogression, and nuclear microsatellite allele sharing was investigated to determine the incidence of nuclear genomic introgression. The cpDNA analyses revealed phylogeographic structuring of eastern and western populations of B. alleghaniensis and B. papyrifera suggesting postglacial colonization from separate refugia. The geographically structured patterns of regional cpDNA haplotype sharing between B. alleghaniensis and B. papyrifera suggest widespread introgression between species during the postglacial recolonization. In contrast, cpDNA markers were monomorphic in B. lenta and no haplotype sharing between B. lenta and other species were detected. Nuclear microsatellite data revealed low levels of population genetic substructure in each of the species with significant differentiation at larger spatial scales due to isolation by \ndistance. The low level of population differentiation over relatively long distances probably reflects the long distance pollen and seed dispersal of these species. The \nanalysis of nuclear microsatellite allele-sharing revealed that despite moderate to high proportions of shared alleles, each of the species was significantly genetically \ndifferentiated. No strong evidence of genetic introgression was found for B. alleghaniensis and B. lenta, or B. papyrifera and B. lenta. Admixture proportions were \nhigher between B. alleghaniensis and B. papyrifera in the western Great Lakes, which is a previously-documented zone of hybridization based on the occurrence of morphological \nintermediates.
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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 | 0.002 | 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".