Pleistocene survival, regional genetic structure and interspecific gene flow among three northern peat‐mosses: <i>Sphagnum inexspectatum</i>,<i> S. orientale</i> and <i>S. miyabeanum</i>
Bibliographic record
Abstract
Abstract Aim Arctic plant species are often characterized by a complex genetic structure because of changes in their population size, the fragmentation of metapopulation systems, extensive hybridization and allopolyploidization, and survival in disjunct refugia, historical features associated with Pleistocene glaciation. We assessed the biogeographical and genetic patterns in three closely related northern species of peat‐moss ( Sphagnum inexspectatum , S. orientale and S. miyabeanum ), especially interspecific hybridization, infraspecific geographical differentiation and Pleistocene survival in one or more refugial areas. We tested alternative hypotheses of refugial survival in three widely disjunct regions: eastern Asia, Alaska and Greenland. Location North America (Canada, western USA and Greenland), China, Japan and Russia. Methods Four hundred and forty‐three plants were genotyped at 12 microsatellite loci. Nucleotide sequences from 130 accessions for two plastid and two nuclear loci were used to reconstruct haplotype relationships. Population genetic analyses produced estimates of genetic diversity, levels of interspecific gene flow and rates of infraspecific intercontinental migration. Approximate Bayesian computation was used to test alternative biogeographical scenarios. Results We found evidence of hybridization between two of the three species, but phylogenetic patterns are predominantly divergent rather than reticulate. Disjunct populations of one species, S. orientale , in Greenland, Alaska and China are genetically differentiated, but migration has occurred among all three metapopulation systems. Divergence‐time analyses strongly support the hypothesis that S. orientale survived the Last Glacial Maximum in Beringia and also in Greenland. Main conclusions Our results indicate that Beringia served as a refugium for peat‐mosses, and therefore peatlands, which are currently extensive at high latitudes of the Northern Hemisphere. Sphagnum orientale also appears to have survived the Last Glacial Maximum in Greenland, indicating that the species persisted in multiple Pleistocene refugia. Phylogenetic patterns are relatively simple in these mosses compared with those commonly encountered in Arctic angiosperms.
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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 | 0.000 | 0.000 |
| 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".