Ontogenetic Shifts in Sex Ratios and the Evolution of Temperature-dependent Sex Determination
Bibliographic record
Abstract
Temperature-dependent sex determination (TSD) exists in all major reptile clades, occurring when incubation temperature determines sex. Theory suggests TSD evolves when incubation temperature differentially influences male versus female fitness. However, TSD’s evolution remains unknown, with difficulty in assessing temperature-by-sex fitness interactions and reconciling confounding TSD types, phylogeny, and life history effects. Based on classical theory, I suggest that since incubation temperature affects condition, TSD evolved so males are produced in high-quality environments. I therefore expect that females suffer greater mortality than males and predict female-biased sex ratios at hatching as compensation, so populations reach even Fisherian sex ratios by adulthood. I test these predictions by examining ontogenetic shifts in sex ratios using a novel dataset in phylogenetically-controlled Bayesian models. I show multiple mechanisms are involved in TSD evolution, with crocodilians and testudines matching my predictions and short-lived reptiles exhibiting the opposite pattern – providing unparalleled insights into the evolution of TSD.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 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 teacher head, 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".