Countergradient Variation in Temperature Preference in Populations of Killifish<i>Fundulus heteroclitus</i>
Bibliographic record
Abstract
Behavioral thermoregulation can allow ectotherms to buffer the effects of changes in environmental temperature, and thus an organism's preferred temperature is thought to be under strong selection. However, this contention has seldom been tested. We used common killifish Fundulus heteroclitus from high-latitude (northern) and low-latitude (southern) populations to investigate intraspecific variation in thermal preference and its relationship to habitat temperature. We quantified the preferred temperatures of northern and southern killifish populations acclimated to three temperatures (5 degrees , 15 degrees , and 25 degrees C) to evaluate two alternative hypotheses for the evolution of differences in thermal preference among latitudinally separated populations: local thermal adaptation, which predicts that organisms from high latitudes should prefer lower temperatures than individuals from lower latitudes, versus countergradient variation, which predicts that high-latitude organisms should prefer higher temperatures to compensate for shorter growing seasons. All killifish selected their final thermal preferendum within 4 h. Southern killifish and killifish acclimated to warmer temperatures had greater variability in selected temperature. This increase in variability was the result of an increase in interindividual variation in preferred temperature rather than a reduction in the precision of temperature selection in these groups. Northern killifish preferred significantly higher temperatures than southern fish (30.6 degrees vs. 29.0 degrees C, respectively, when calculated on the basis of the temperature selected consistently for at least 30 min; 28.4 degrees vs. 26.5 degrees C, respectively, when calculated on the basis of the mean temperature occupied), regardless of acclimation temperature. These data are not consistent with local adaptation in thermal preference but instead can be better explained by countergradient variation in thermal preference in killifish.
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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 | 0.000 | 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) | 0.000 | 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".