Evolution of sexual colour pattern dimorphism in the ambush bug Phymata americana
Bibliographic record
Abstract
The occurrence of sex differences in trait expression (i.e. sexual dimorphism), especially cases where the trait appears to be exaggerated, represent some of the most spectacular examples of diversity within and among species. While evolutionary biologists typically invoke selection as the cause of such diversity, sufficient demonstrations of the role of selection for shaping this variation in nature remain elusive. Here, I investigated the possible role of selection for the evolution of sexual dimorphism in colour pattern in the ambush bug Phymata americana, an insect species in which males exhibit heightened expression of certain components of dark colouration. I show that increased levels of pigmentation result in higher mating success in wild males, indicating that contemporary sexual selection pressures can account for the observed sexual dimorphism. While the direction and form of sexual selection varied considerably within and between years, the strength of sexual selection covaried strongly with demographic factors, consistent with the notion that ecological factors play a crucial role in determining the relative fitness of phenotypes. Investigation of the mechanisms underlying sexual selection suggest that colour pattern played no role in mediating direct male-male interactions or male-female interactions. Instead, experiments provided evidence to support the novel hypothesis that sexual selection in this species is mediated by the effects of colour pattern on thermoregulatory performance and, consequently, mate searching success. While the benefit (for males) of increased pigmentation is clear, the persistence of trait variation in males and the absence/reduction of pigmentation in females suggests substantial fitness costs associated with colour pattern. I tested the prediction that sexually selected male traits should exhibit heightened sensitivity to resource availability (i.e. condition dependence) relative to non-sexually selected traits. In accord with this prediction, experimental manipulation of resource availability revealed that males in high condition were able to achieve greater trait expression than did their poor-condition counterparts. Furthermore, increased resource availability had positive effects on female lifespan but negative effects on male lifespan, suggesting a trade-off in males, between allocation to the sexually selected trait and allocation to survivorship.
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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 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".