Repeated climate-driven dispersal and speciation in peripheral populations of Pleistocene mastodons
Bibliographic record
Abstract
Abstract Recent ancient DNA work has shed some light on the responses of mastodons to Pleistocene glacial/interglacial cycling but focused primarily on their expansion into Beringia. However, genetics has complicated our understanding of the relationships within Mammut , specifically between Pacific and American mastodon phylogeography and questioned whether these are in fact two separate species or regionally localized morphotypes. Here we expand on both avenues by sequencing and contextualizing the mitochondrial genome of a Pacific mastodon, as well as from several North American eastern specimens throughout the last 800 thousand years. We show that Pacific mastodons fall within a previously established, and deeply divergent mitochondrial clade, extending the range of this species into western Canada and potentially Mexico. We also present evidence for at least three discrete expansion events into northeastern coastal regions (i.e. Nova Scotia and the eastern continental shelf), and identify two new mastodon clades, which contain temporally distinct, but geographically co-occurrent specimens. This work sheds further light on mastodon taxonomy and phylogeography across North America throughout the Pleistocene, highlighting interglacial range expansion into northeastern America mirroring the effects on the western side of the continent (Beringia).
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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".