Evolution and Ecological Consequences of Temperature-Dependent Sex Determination in Long-Lived Reptiles
Bibliographic record
Abstract
Temperature exerts strong and pervasive effects on reptile development, resulting in lasting phenotypic impacts and consequences for individual fitness. An interesting example of pervasive effects of early-life temperature is in temperature-dependent sex determination (TSD), whereby incubation temperature irreversibly determines an individual’s sex. TSD has been described in 137 reptile species, but we have no taxonomically widespread explanation for its adaptive significance. Nor do we understand how TSD may have persisted through climatic upheaval in deep time. My thesis addresses both key questions.The adaptive significance of TSD is likely rooted in the Charnov-Bull model, which states that TSD is adaptive if the ratio of male to female fitness varies with temperature. This model predicts a sex-by-temperature interaction on offspring fitness, but given the diversity of reptile natural histories, it is not clear how this interaction could manifest in a manner that is taxonomically widespread. I test three hypotheses for the driver underlying this interaction: 1) immune system strength; 2) an extension of the Trivers-Willard hypothesis (males should be produced in high-quality environments as their fitness is strongly dependent on condition); 3) the Survival to Maturity hypothesis (sex differences in age at maturity compound survival differences resulting from incubation temperatures). I find that the Survival to Maturity hypothesis is consistent with the results of my thesis. Given that sex is determined by temperature, widespread feminization of populations is predicted under climate change. However, our knowledge of how climate change will affect species with TSD is limited to species with MF TSD (males produced at cool temperatures and females at warm temperatures). To address this gap, I investigate long-term trends in primary sex ratios of snapping turtles (Chelydra serpentina), an FMF TSD species. Despite documented warming, the sex ratio remained unchanged over 21 years in Algonquin Park, Canada. I attribute this resilience to remarkable intra-annual variation in sex ratio which is, in turn, related to individual-level attributes of nests that affect development temperature. My thesis provides further direction for tests into the adaptive significance of TSD and suggests that aspects of TSD and species biology contribute to resilience to climate change.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".