The effects of sympatry on patterns of bill morphology between closely related species of birds, worldwide
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Bibliographic record
Abstract
When closely related species co-occur in sympatry, they face a significant challenge.They must adapt to the same local conditions in their shared environment, which favours the convergent evolution of traits, while simultaneously minimizing the costs of competition for shared resources that typically favours the divergent evolution of traits.Here, we use a comparative sister lineage approach to test how most species have responded to these conflicting selection pressures in sympatry, focusing on a key ecological trait: the bill morphology of birds.If similar bill morphologies incur fitness costs due to species interactions, then we predicted that the bill morphologies of closely related species would differ more in sympatry compared with allopatry.Alternatively, if similar bill morphologies incur fitness benefits due to local adaptation, then we predicted that the bill morphologies would be more similar in sympatry compared with allopatry.We used museum specimens to measure five aspects of bill (maxilla) morphologydepth, length, width, side shape, and bottom shapein diverse bird species from around the world to test our alternative hypotheses.We found support for both divergent evolution and convergent evolution (or trait retention) in one ecological trait: closely related sympatric species diverged in bill depth, but converged in side shape.These patterns of bill evolution were influenced by the genetic distance between closely related sister taxa and the geographic distance between allopatric lineages.Overall, our results highlight species interactions as an important mechanism for the evolution of some (bill depth), but not all (bill shape), aspects of bill morphology in closely related species in sympatry, and provide strong support for the bill as a key ecological trait that can adapt in different ways to the conflicting challenges of sympatry.
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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 | 0.001 |
| 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 it