Evolvability and the Diversification of the Craniofacial Skeleton in the Domesticated Pigeon ( <i>Columba livia</i> )
Bibliographic record
Abstract
The elucidation of the mechanisms underlying the evolution of complex structures, like the cranium, represents a principal aim in evolutionary biology. It has been argued that the evolution of a modular organization, by which different subunits of a structure can change relatively independent from one another, has favored the morphological diversification of complex structures. However, the potential of species to diversify can be hidden in natural populations due to the fact that both natural selection and genetic drift tend to reduce phenotypic variation. This mismatch between potential and actual phenotypic variation will confound studies aimed to understand the role of integration and modularity in the evolution of complex structures. For example, a taxon with a high degree of modularity could display lower phenotypic variation than a taxon with low modularity if the former evolved under strong stabilizing selection. Domesticated species are characterized for displaying a wider spectrum of morphologies than their wild populations. Thus, domesticated species offer a unique opportunity to investigate if this increase in phenotypic diversification is related to changes in pattern and/or magnitude of morphological integration and modularity or, instead, it reflects the potential of a common structural pattern to generate phenotypic variation, i.e. the evolvability of the wild population. Here we use geometric morphometrics to quantify variation in cranium size and shape of domesticated pigeons and compare this to their feral counterparts. We show that domesticated pigeons do not represent novel phenotypes but extensions of variation already present in the feral population. We also show that the increase of variation in domesticated pigeons would mainly reflect the evolvability of the feral population. Support or Funding Information National Institutes of Health Grants R01DE019638 and R01DE021708.
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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 | 0.001 | 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 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".