Pronghorn (Antilocapra americana) enamel phosphate δ18O values reflect climate seasonality: implications for paleoclimate reconstruction
Bibliographic record
Abstract
Stable oxygen isotope compositions from vertebrate tooth enamel are commonly used as biogeochemical proxies for paleoclimate reconstructions. However, the utility of enamel isotopic values across species varies due to differences in rates of enamel deposition and mineralization as well as sources of ingested water, body water residence times, and species' physiology. We evaluate the use of stable oxygen isotope compositions from pronghorn (Antilocapra americana Gray, 1866) enamel for the amplitude reconstruction of terrestrial paleoclimate seasonality. We serially sampled the third lower molars of pronghorn from Wyoming for oxygen isotope composition in phosphate (δ18OPO4) and compared patterns to: (1) interpolated and (2) measured yearly variation in central Wyoming environmental waters (δ18Ow) as well as to (3) δ18O values from sagebrush leaves and stems in the same region. Although we recognize the numerous factors influencing the composition of mammal body water, our null hypothesis was that δ18OPO4 enamel values reflect δ18Ow with a constant offset due to mammalian physiology. We set up our null hypothesis by converting δ18Ow values to δ18OPO4 using a published regression based on empirical results from mammals. Pronghorn δ18OPO4 values from enamel are consistently enriched in 18O relative to the predicted values. We hypothesized that pronghorn δ18OPO4 values might also reflect dietary water and therefore also converted δ18Oleaf values from plants into predicted δ18OPO4 values. We infer that pronghorn obtain at least some of their water from 18O-enriched plants because pronghorn enamel δ18OPO4 values are more similar to predicted δ18OPO4 values from plants than from meteoric waters. Modeling of source body water δ18O values show amplitudes between 70% and 95% of seasonal variation from Wyoming δ18Ow values. Collectively, our findings establish that modern seasonality in source water is reliably reflected in modern pronghorn enamel providing the basis for exploring changes in the amplitude of seasonality of ancient climates using archived tooth collections.
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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 | 0.001 |
| 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".