Assessing niche differences of sex, armour and asymmetry phenotypes using stable isotope analyses
Bibliographic record
Abstract
Identifying phenotype-specific selective landscapes within populations continues to challenge evolutionary biologists in studies of adaptive variation. We explore here the potential applica-tion of carbon and nitrogen stable isotope ratios of tissues as time-integrated proxies of niche space among sex, armour and asymmetry phenotypes within an endemic population of gi-ant threespine stickleback from Haida Gwaii, western Canada. Muscle tissues were extracted from 289 stickleback collected from Drizzle Lake, taken in transects during June 1981, June 1982, September 1982 and June 1983 and isotopic ratios of 15N/14N (δ15N) and 13C/12C (δ13C) determined by continuous-flow isotope ratio mass spectrometry. Among all fish, δ15N values, which reflect relative trophic level, ranged from 6.5 to 10.6 while δ13C, which reflects reliance on different carbon pathways of primary producers, ranged from −30.5 to −27.5. The sexes did not differ in δ15N but females were significantly enriched in δ13C rel-ative to males among all samples. In each transect, lateral plate phenotypes differed in δ15N, with higher plate counts generally enriched in 15N. δ13C did not vary among plate pheno-types. Approximately 50 % of the adult population exhibit lateral plate asymmetries usually with one plate different between sides. Sticklebacks that were asymmetric (absolute asym-metry) did not differ from symmetric fish for either δ15N or δ13C signatures. However, this result masked a significant and consistent effect of signed asymmetries (right side − left side), with δ15N enrichment among right-biased compared to left-biased asymmetric. These unex-pected results indicate the presence of subtle and previously unrecognized niche differences in lateral plate number and asymmetry phenotypes and are consistent with the predictions of niche-width and adaptive variation hypotheses. The results also suggest the wider application of isotopic techniques to elucidate phenotype-specific ecological and selective landscapes. 1) Corresponding author’s
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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 | 0.001 |
| Science and technology studies | 0.001 | 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".