MATING SYSTEMS, SPERM COMPETITION, AND THE EVOLUTION OF SEXUAL DIMORPHISM IN BIRDS
Why this work is in the frame
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Bibliographic record
Abstract
Comparative analyses suggest that a variety of factors influence the evolution of sexual dimorphism in birds. We analyzed the relative importance of social mating system and sperm competition to sexual differences in plumage and body size (mass and tail and wing length) of more than 1,000 species of birds from throughout the world. In these analyses we controlled for phylogeny and a variety of ecological and life-history variables. We used testis size (corrected for total body mass) as an index of sperm competition in each species, because testis size is correlated with levels of extrapair paternity and is available for a large number of species. In contrast to recent studies, we found strong and consistent effects of social mating system on most forms of dimorphism. Social mating system strongly influenced dimorphism in plumage, body mass, and wing length and had some effect on dimorphism in tail length. Sexual dimorphism was relatively greater in species with polygynous or lekking than monogamous mating systems. This was true when we used both species and phylogenetically independent contrasts for analysis. Relative testis size was also related positively to dimorphism in tail and wing length, but in most analyses it was a poorer predictor of plumage dimorphism than social mating system. There was no association between relative testis size and mass dimorphism. Geographic region and life history were also associated with the four types of dimorphism, although their influence varied between the different types of dimorphism. Although there is much interest in the effects of sperm competition on sexual dimorphism, we suggest that traditional explanations based on social mating systems are better predictors of dimorphism in birds.
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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 | 0.000 |
| 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 it